Health Education
Health education is "any combination of learning experiences designed to facilitate voluntary actions conducive to health."
Health education is defined as the process by which individuals and groups of people learn to behave in a manner conducive to the promotion, maintenance or restoration of health.
Wednesday, January 2, 2008
Tuesday, January 1, 2008
EPIDEMILOGY OF COMMUNICABLE DISEASES
HIV/AIDS
AIDS is a fatal disease caused by human immunodeficiency virus characterized by profound immunosuppression associated with opportunistic infection, the development of certain tumors (Kaposi’s sarcoma) and frequent involvement of the CNS. Strictly speaking, the term AIDS refers only to the last stage of the HIV infection.
PREVENTION AND CONTROL MEASURES
A. Treatment: There is no specific treatment for HIV/AIDS infection. Certain antiviral drugs are available- Zidovudine, gamma interferon, ribavarin etc.
B. Control: 1. Modification of human behavior regarding
a) Sexual behavior- Avoidance of sexual contact with multiple partners, avoidance of unprotected sexual intercourse, avoidance of high risk activities- anal sex, regular venereological screening for high risk group- prostitutes.
b) Blood transfusion- Screening of donated blood.
c) Contaminated needles and other equipments- Use of disposable syringe and other equipments.
d) Perinatal infection- Infected women of childbearing age should be counseled on avoidance of pregnancy through the use of contraceptives.
2. Counseling of persons found to be antibody positive- Regular medical evaluation and follow up are advised.
3. Health education- To educate the public about the modes of transfusion, to educate the public about safe sex.
C. Surveillance: Collecting and analyzing relevant data about infection in the population, the prevalence and distribution of the infection, the high risk group, patterns of behavior, community attitude to AIDS and the patients.
HIV/AIDS IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• 1st case of HIV detected in 1989.
• Since than total cumulative of 1207 cases of HIV have been confirmed as of 1st December 2007
• 365 have developed AIDS out of whom 123 died
• During 1st December 2007 to 1st December 2007 a total 333 new HIV infection recorded & reported.
• The estimated total number of people living with HIV/AIDS in Bangladesh is around 7,500
• In all 7 rounds of serological surveillance it found that HIV rates have remained below 1% in all ground except in IDUs.
• Among the IDUs prevalence reached from 1.4% in 2000 to 7% in 2006 which is a level closed to concentrated epidemic.
• 7th surveillance shows significant rated of active syphilis among FSWs (1-10%), msm (4-6%) IDUs (1-9%)
HEPATITIS B
Hepatitis B is an acute systemic infection caused by hepatitis B virus which is characterized by long incubation period and which is life threatening. Hepatitis B may occur around the year and it has no seasonal pattern.
High risk group- Surgeons, physician, dentists, nurses, blood bank and hospital personnel, recipients of blood transfusion, homosexuals, prostitutes etc.
PREVENTION AND CONTROL MEASURES
A. Diagnosis: 1. Clinical 2. Lab diagnosis- Immunoassay for HBsAg.
B. Isolation: A patient should be isolated and put on rest.
C. Treatment: No specific treatment for acute or chronic HBV infection, exists although alpha interferon hold some promise.
D. Prevention: 1. Immunization: a) Active- By hepatitis B vaccine. The vaccine consists of HBsAg, each 1 ml dose of the vaccine contains 20 microgram of HBsAg. b) Passive- By hepatitis B immunoglobulin (HBIG). It should be given for immediate protection within 24 hour or almost a week in following circumstances: i) Accidental needle puncture ii) Gross personal contamination with infected blood iii) Newborn infants of carrier mother iv) Sexual contact of acute hepatitis B virus. c) Active-Passive- By simultaneous use of Hepatitis B vaccine and HBIG at separate sites.
2. Specific control measure: i) All person donating blood should be investigated the presence of Hepatitis B virus. ii) Needle, syringe should be properly sterilized before use. iii) Best method is to use disposable syringe and needle. iv) Persons who are at risk(doctors, nurses) all of them should be given HBIG to develop passive immunization.
HEPATITIS B IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• It is indeed scary news that more than 80 per cent of the total demand of blood in Bangladesh comes from professional blood donors, most of whom suffer from various blood-borne diseases like Hepatitis, HIV and Sexually Transmitted Infections (STIs).
• According to World Health Organization (WHO), transfusion-transmitted infections (TTIs) remains a major public health problem in the country as the demand for blood transfusions is mostly met by unscreened contaminated blood collected from professional donors on payment.
• Poverty, poorly managed commercial blood banks (less sensitive screening and lack of quality control) and an increasing trend in drug addiction and prostitution are listed as the main causes of the prevalence hepatitis B virus (HBV) in professional donors. In 2001 WHO ranked Bangladesh in the moderate-to high-risk group of countries for HBV infection.
MEASLES
Measles is an acute inflammatory disease caused by a paramyxovirus which presents with respiratory catarrhal symptoms (fever, Koplik’s spots on buccal mucosa) and a characteristic skin rash. Maternal antibody gives protection for the first 6 months of life. Measles is a serious disease in the malnourished, vitamin deficient or immunocompromised.
PREVENTION AND CONTROL MEASURES
A. Diagnosis: Clinical: 1. Prodromal phase (Catarrhal stage): This is characterized by- Fever, Sneezing, Conjunctivitis, Coughing, Hoarseness of voice, Koplik’s spots- bright red lesions with a white, central spot that are located on the buccal mucosa and are virtually diagnostic of measles. They last for 3 or 4 days. 2. Exanthematous stage: This stage is characterized by- Dark red macular or maculopapular rash- It develops first at the back of the ears and at the junction of the forehead and the hair. Within a few hours the rash proceeds gradually down the body to the lower extremities.
Laboratory Diagnosis: a) Blood count- Leukocytosis in the early stages followed by an increase in lymphocytes. b) Sputum or urine culture- Stained smears show large multinucleate (giant) cells.
B. Isolation: All patients should be isolated for 10 days from the appearance of the rash.
C. Treatment: Antiviral therapy- Not available. Antibiotics- It should be given only if a
child has clinical signs of pneumonia or other evidence of sepsis.
D. Prevention: i) Active immunization- A children should be protected by measles intramuscularly or subcutaneously at deltoid region. ii) Passive immunization- with human gamma globulin 0.25 mg/kg is effective if given within 3 days of exposure.
MEASLES IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• In 1984 before EPI intensification 2.6 million children suffered from measles
• In 1999 number of cases dropped to 1 million
• In 2003 no of measles cases were 4505
• In 2004 no of measles cases were 10090
• In 2005 no of measles cases were 28370
• In 2007 no of measles outbreaks were 292
• Around 20,000 children died from measles complication every year until 2005.
• Measles immunization coverage is also poor which was 78% in 2006
• Global Death of Measles fell by 48% from 1999 to 2004
• Deaths reduced from 8.7 million in 1999 to 4.5 million in 2004
• 4.1 million are children out of 4.5 million died
• >95% of Measles death occurred in countries having GNI less than $1000
• 47 Countries account for about 98% of global measles deaths
HOOKWORM INFECTION
Hookworm infection is a chronic debilitating disease caused by soil transmitted helminthes A. duodenale and N. americanus, clinically characterized by anemia (microcytic hypochromic). It is more common in the countries of low socio-economic status where disposal of excreta is not sanitary. A. duodenale infection is common in Bangladesh.
PREVENTION AND CONTROL MEASURES
A. Diagnosis: 1. Clinical 2. Laboratory- a) Finding of hookworm eggs in feces b) Occult blood test- should be positive c) Blood test for anemia
B. Control: Control of hookworm infection involves 4 approaches- 1. Sanitary disposal of feces 2. Health education with community participation 3. Chemotherapy 4. Correction of anemia.
1. Sanitation and health education-
• The provision of latrine and education in their proper usage are crucial to the control of hookworm infection.
• Fecal contamination of soil must be prevented.
• Wearing of shoes to protect the feet
• Wearing of hand gloves when handling suspected things polluted with the hookworm larvae.
2. Chemotherapy-
a) Treatment strategy- Mass treatment of whole community selective chemotherapy of all those infected.
b) Drugs-
• Tab. Mebendazol (100 mg) twice daily for 3 days. Most effective for the treatment of hookworm infection.
• Tab. Albendazol (400 mg) in a single dose for all ages over 1 yr.
• Tab. Pyrantel (10 mg/kg) in a single dose for 3 days.
3. Correction of anemia- Ferrous sulphate (200 mg) thrice daily by mouth for 3 months till hemoglobin concentration has risen to 12g /100 ml.
HOOKWORM INFECTION IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• The latest evidence confirms that blood loss caused by the worms' feeding activity in the gut is a contributing factor in the development of poor iron status leading to iron-deficiency anemia.
• The World Health Organization has identified adolescent girls and women of child-bearing age as high-risk groups regarding the impact of hookworm disease.
• Treating pregnant women with anthelminthic drugs after the first trimester is very much useful to prevent future sufferings from iron deficiency anemia.
CHOLERA
Cholera is an acute diarrheal disease caused by V. cholerae classically characterized by sudden onset of profuse, effortless, watery diarrhea followed by vomiting, marked dehydration, muscular cramps and suppression of urine.
PREVENTION AND CONTROL MEASURES
A. Notification- Cholera is an internationally notifiable disease.
B. Diagnosis: i) Clinical diagnosis ii) Lab diagnosis: a. M/E of Stool- under DGI will show shooting star appearance b. Culture of the Stool
C. Isolation: All cases should be isolated in ICDDRB until at least 3 culture examination are negative.
D. Disinfection: All contaminated articles disinfected by phenols, boiling or lime.
E. Treatment: 1. Rehydration therapy: Prevention and management of dehydration-home-based fluids, ORS, IV fluids. Continued feeding. 2. Drug Treatment: Use of an effective antimicrobial drug e.g. Doxycycline, Erythromycin, Azithromycin, Newer quinolones (Cipro, Norflox) etc.
F. Prevention:
1. Personal prophylaxis and public health measures:
a. Improved sanitation- Provision of safe drinking water, satisfactory sanitary disposal of excreta, refuse & sewage, protection of Foods, house fly control measures.
b. Health education: To drink safe water from tube well, otherwise boiled water or tablet treated water, avoid hot & rotten food and raw vegetables, good hygiene should be maintained.
2. Chemoprophylaxis: Mass treatment with Tetracycline.
3. Vaccination: Cholera vaccine 50% effective in preventing disease for 3-6 months.
CHOLERA IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• Lack of safe drinking water and inadequate safe drinking water supply system.
• High density of population
• Unsatisfactory unhygienic disposal of excreta and refuse
• Cholera is endemic in Bangladesh with periodic epidemic outbreaks- does not report to WHO.
• V. cholerae infection causes the most severe form of secretory diarrheas.
• New serotype V. cholerae O139
• ICDDR,B hosts the only hospital by the name “CHOLERA HOSPITAL” that treats about 1 million diarrheal patients per year.
• About 30% of them are adults.
• During the epidemic situation more than 50% of the adults suffer from cholera.
• Can be fatal if left untreated.
• 10% develop typical severe cholera
• Case fatality: <1%>
AIDS is a fatal disease caused by human immunodeficiency virus characterized by profound immunosuppression associated with opportunistic infection, the development of certain tumors (Kaposi’s sarcoma) and frequent involvement of the CNS. Strictly speaking, the term AIDS refers only to the last stage of the HIV infection.
PREVENTION AND CONTROL MEASURES
A. Treatment: There is no specific treatment for HIV/AIDS infection. Certain antiviral drugs are available- Zidovudine, gamma interferon, ribavarin etc.
B. Control: 1. Modification of human behavior regarding
a) Sexual behavior- Avoidance of sexual contact with multiple partners, avoidance of unprotected sexual intercourse, avoidance of high risk activities- anal sex, regular venereological screening for high risk group- prostitutes.
b) Blood transfusion- Screening of donated blood.
c) Contaminated needles and other equipments- Use of disposable syringe and other equipments.
d) Perinatal infection- Infected women of childbearing age should be counseled on avoidance of pregnancy through the use of contraceptives.
2. Counseling of persons found to be antibody positive- Regular medical evaluation and follow up are advised.
3. Health education- To educate the public about the modes of transfusion, to educate the public about safe sex.
C. Surveillance: Collecting and analyzing relevant data about infection in the population, the prevalence and distribution of the infection, the high risk group, patterns of behavior, community attitude to AIDS and the patients.
HIV/AIDS IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• 1st case of HIV detected in 1989.
• Since than total cumulative of 1207 cases of HIV have been confirmed as of 1st December 2007
• 365 have developed AIDS out of whom 123 died
• During 1st December 2007 to 1st December 2007 a total 333 new HIV infection recorded & reported.
• The estimated total number of people living with HIV/AIDS in Bangladesh is around 7,500
• In all 7 rounds of serological surveillance it found that HIV rates have remained below 1% in all ground except in IDUs.
• Among the IDUs prevalence reached from 1.4% in 2000 to 7% in 2006 which is a level closed to concentrated epidemic.
• 7th surveillance shows significant rated of active syphilis among FSWs (1-10%), msm (4-6%) IDUs (1-9%)
HEPATITIS B
Hepatitis B is an acute systemic infection caused by hepatitis B virus which is characterized by long incubation period and which is life threatening. Hepatitis B may occur around the year and it has no seasonal pattern.
High risk group- Surgeons, physician, dentists, nurses, blood bank and hospital personnel, recipients of blood transfusion, homosexuals, prostitutes etc.
PREVENTION AND CONTROL MEASURES
A. Diagnosis: 1. Clinical 2. Lab diagnosis- Immunoassay for HBsAg.
B. Isolation: A patient should be isolated and put on rest.
C. Treatment: No specific treatment for acute or chronic HBV infection, exists although alpha interferon hold some promise.
D. Prevention: 1. Immunization: a) Active- By hepatitis B vaccine. The vaccine consists of HBsAg, each 1 ml dose of the vaccine contains 20 microgram of HBsAg. b) Passive- By hepatitis B immunoglobulin (HBIG). It should be given for immediate protection within 24 hour or almost a week in following circumstances: i) Accidental needle puncture ii) Gross personal contamination with infected blood iii) Newborn infants of carrier mother iv) Sexual contact of acute hepatitis B virus. c) Active-Passive- By simultaneous use of Hepatitis B vaccine and HBIG at separate sites.
2. Specific control measure: i) All person donating blood should be investigated the presence of Hepatitis B virus. ii) Needle, syringe should be properly sterilized before use. iii) Best method is to use disposable syringe and needle. iv) Persons who are at risk(doctors, nurses) all of them should be given HBIG to develop passive immunization.
HEPATITIS B IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• It is indeed scary news that more than 80 per cent of the total demand of blood in Bangladesh comes from professional blood donors, most of whom suffer from various blood-borne diseases like Hepatitis, HIV and Sexually Transmitted Infections (STIs).
• According to World Health Organization (WHO), transfusion-transmitted infections (TTIs) remains a major public health problem in the country as the demand for blood transfusions is mostly met by unscreened contaminated blood collected from professional donors on payment.
• Poverty, poorly managed commercial blood banks (less sensitive screening and lack of quality control) and an increasing trend in drug addiction and prostitution are listed as the main causes of the prevalence hepatitis B virus (HBV) in professional donors. In 2001 WHO ranked Bangladesh in the moderate-to high-risk group of countries for HBV infection.
MEASLES
Measles is an acute inflammatory disease caused by a paramyxovirus which presents with respiratory catarrhal symptoms (fever, Koplik’s spots on buccal mucosa) and a characteristic skin rash. Maternal antibody gives protection for the first 6 months of life. Measles is a serious disease in the malnourished, vitamin deficient or immunocompromised.
PREVENTION AND CONTROL MEASURES
A. Diagnosis: Clinical: 1. Prodromal phase (Catarrhal stage): This is characterized by- Fever, Sneezing, Conjunctivitis, Coughing, Hoarseness of voice, Koplik’s spots- bright red lesions with a white, central spot that are located on the buccal mucosa and are virtually diagnostic of measles. They last for 3 or 4 days. 2. Exanthematous stage: This stage is characterized by- Dark red macular or maculopapular rash- It develops first at the back of the ears and at the junction of the forehead and the hair. Within a few hours the rash proceeds gradually down the body to the lower extremities.
Laboratory Diagnosis: a) Blood count- Leukocytosis in the early stages followed by an increase in lymphocytes. b) Sputum or urine culture- Stained smears show large multinucleate (giant) cells.
B. Isolation: All patients should be isolated for 10 days from the appearance of the rash.
C. Treatment: Antiviral therapy- Not available. Antibiotics- It should be given only if a
child has clinical signs of pneumonia or other evidence of sepsis.
D. Prevention: i) Active immunization- A children should be protected by measles intramuscularly or subcutaneously at deltoid region. ii) Passive immunization- with human gamma globulin 0.25 mg/kg is effective if given within 3 days of exposure.
MEASLES IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• In 1984 before EPI intensification 2.6 million children suffered from measles
• In 1999 number of cases dropped to 1 million
• In 2003 no of measles cases were 4505
• In 2004 no of measles cases were 10090
• In 2005 no of measles cases were 28370
• In 2007 no of measles outbreaks were 292
• Around 20,000 children died from measles complication every year until 2005.
• Measles immunization coverage is also poor which was 78% in 2006
• Global Death of Measles fell by 48% from 1999 to 2004
• Deaths reduced from 8.7 million in 1999 to 4.5 million in 2004
• 4.1 million are children out of 4.5 million died
• >95% of Measles death occurred in countries having GNI less than $1000
• 47 Countries account for about 98% of global measles deaths
HOOKWORM INFECTION
Hookworm infection is a chronic debilitating disease caused by soil transmitted helminthes A. duodenale and N. americanus, clinically characterized by anemia (microcytic hypochromic). It is more common in the countries of low socio-economic status where disposal of excreta is not sanitary. A. duodenale infection is common in Bangladesh.
PREVENTION AND CONTROL MEASURES
A. Diagnosis: 1. Clinical 2. Laboratory- a) Finding of hookworm eggs in feces b) Occult blood test- should be positive c) Blood test for anemia
B. Control: Control of hookworm infection involves 4 approaches- 1. Sanitary disposal of feces 2. Health education with community participation 3. Chemotherapy 4. Correction of anemia.
1. Sanitation and health education-
• The provision of latrine and education in their proper usage are crucial to the control of hookworm infection.
• Fecal contamination of soil must be prevented.
• Wearing of shoes to protect the feet
• Wearing of hand gloves when handling suspected things polluted with the hookworm larvae.
2. Chemotherapy-
a) Treatment strategy- Mass treatment of whole community selective chemotherapy of all those infected.
b) Drugs-
• Tab. Mebendazol (100 mg) twice daily for 3 days. Most effective for the treatment of hookworm infection.
• Tab. Albendazol (400 mg) in a single dose for all ages over 1 yr.
• Tab. Pyrantel (10 mg/kg) in a single dose for 3 days.
3. Correction of anemia- Ferrous sulphate (200 mg) thrice daily by mouth for 3 months till hemoglobin concentration has risen to 12g /100 ml.
HOOKWORM INFECTION IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• The latest evidence confirms that blood loss caused by the worms' feeding activity in the gut is a contributing factor in the development of poor iron status leading to iron-deficiency anemia.
• The World Health Organization has identified adolescent girls and women of child-bearing age as high-risk groups regarding the impact of hookworm disease.
• Treating pregnant women with anthelminthic drugs after the first trimester is very much useful to prevent future sufferings from iron deficiency anemia.
CHOLERA
Cholera is an acute diarrheal disease caused by V. cholerae classically characterized by sudden onset of profuse, effortless, watery diarrhea followed by vomiting, marked dehydration, muscular cramps and suppression of urine.
PREVENTION AND CONTROL MEASURES
A. Notification- Cholera is an internationally notifiable disease.
B. Diagnosis: i) Clinical diagnosis ii) Lab diagnosis: a. M/E of Stool- under DGI will show shooting star appearance b. Culture of the Stool
C. Isolation: All cases should be isolated in ICDDRB until at least 3 culture examination are negative.
D. Disinfection: All contaminated articles disinfected by phenols, boiling or lime.
E. Treatment: 1. Rehydration therapy: Prevention and management of dehydration-home-based fluids, ORS, IV fluids. Continued feeding. 2. Drug Treatment: Use of an effective antimicrobial drug e.g. Doxycycline, Erythromycin, Azithromycin, Newer quinolones (Cipro, Norflox) etc.
F. Prevention:
1. Personal prophylaxis and public health measures:
a. Improved sanitation- Provision of safe drinking water, satisfactory sanitary disposal of excreta, refuse & sewage, protection of Foods, house fly control measures.
b. Health education: To drink safe water from tube well, otherwise boiled water or tablet treated water, avoid hot & rotten food and raw vegetables, good hygiene should be maintained.
2. Chemoprophylaxis: Mass treatment with Tetracycline.
3. Vaccination: Cholera vaccine 50% effective in preventing disease for 3-6 months.
CHOLERA IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• Lack of safe drinking water and inadequate safe drinking water supply system.
• High density of population
• Unsatisfactory unhygienic disposal of excreta and refuse
• Cholera is endemic in Bangladesh with periodic epidemic outbreaks- does not report to WHO.
• V. cholerae infection causes the most severe form of secretory diarrheas.
• New serotype V. cholerae O139
• ICDDR,B hosts the only hospital by the name “CHOLERA HOSPITAL” that treats about 1 million diarrheal patients per year.
• About 30% of them are adults.
• During the epidemic situation more than 50% of the adults suffer from cholera.
• Can be fatal if left untreated.
• 10% develop typical severe cholera
• Case fatality: <1%>
• Can kill an adult in 2-4 hours
MALARIA
Malaria is a disease of wide distribution caused by sporozoa of the genus plasmodium characterized by paroxysmal fever with periods of latency, enlargement of spleen and secondary anaemia.
There are 4 species of malarial parasites which infect humans:
• P. falciparum. This species, predominant in Africa, produces the most severe symptoms and is responsible for most malaria deaths.
• P. vivax. This species, found mostly in tropical areas of Asia, produces less severe symptoms but can remain in your liver and cause relapses for up to three years.
• P. malariae. This species found in Africa, can cause typical malaria symptoms, but on rare occasions it can remain in bloodstream.
• P. ovale. This species is found mostly in West Africa. Although rare, it can also cause relapses.
PREVENTION AND CONTROL MEASURES
A. The individual: Chemoprophylaxis: the antimalarial available for chemoprophylaxis are proguanil, Chloroquine, Maloprim, Mefloquine.
B. The Vector: attempted in two ways- 1. Adult mosquito Control: by insecticides varies from area to area. 2. Prevention of mosquito breeding by larval control: heavy oiling with antimalarial oil &insecticides, spraying with 5 % DDT.
C. The community: Active community participation is important. The measures to be applied by locally recruited and trained workers include- residual spraying, larviciding, mass drug administration.
D. Prevention:
• There's no effective vaccine against malaria.
• In countries where the disease is endemic, prevention involves keeping mosquitoes away from humans. This has included the use of insecticide-treated mosquito netting and spraying indoor walls with insecticide.
• Most drugs used to treat malaria are also used to prevent it. Doctors sometimes use the antibiotic doxycycline to prevent malaria. Tips to prevent malaria: The CDC also recommends the following measures to help prevent malaria:
• Use repellent. Spray DEET insect repellent on exposed skin, and use flying-insect spray to kill mosquitoes in your sleeping area. • Wear protective clothing. During active mosquito times, usually from dusk to dawn, wear pants and long-sleeved shirts. • Use netting. If you're staying in a place that doesn't have screens or air conditioning, sleep under mosquito netting that's been treated with an insecticide called permethrin. This netting is available in many travel and camping supply stores and online.
MALARIA IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• In Bangladesh, it is mainly caused by the female Anopheles mosquitoes.
• The disease restricted to areas where the females Anopheles mosquitoes can bread.
• Malaria is now on the increase due to emergence of drug resistance.
• Presence of extra human reservoir of infection.
• Common border of Bangladesh & India: disease agent can cross the border & cause malaria of the people of the border area.
• Hilly areas are covered with dense forest where operation could not carried out properly.
• Migratory habit of the people
• Poor standard of environmental sanitation.
TYPHOID FEVER
Typhoid is an infectious and communicable disease caused by gram negative bacillus Salmonella typhi, characterized by headache, high fever, malaise, anorexia, abdominal discomfort and pt. is very much toxic. The disease is also known as Enteric fever - as because, it affects gastrointestinal tract. The disease also affects Liver, Kidneys, Lungs, Heart, and Lymph nodes & Glands.
PREVENTION AND CONTROL MEASURES
A. Notification
B. Diagnosis: i) Clinical ii) Laboratory- a. Blood culture: in MacConkey’s agar media- Positive at 1st week b. Stool culture: in MacConkey’s agar media, DCA-Positive from 2nd or 3rd week c. Urine culture: in MacConkey’s agar media- Positive in 2nd, 3rd or 4th week d. Serological test: Widal test - Positive during 2nd week e. Phage typing of isolated strains f. Routine blood test: TC - Leucopenia, DC - Neutropenia
C. Isolation: Case should be isolated till “3” negative stools and urine culture reports are obtained on three separate days.
D. Disinfection: Stools and urine should be disinfected with 5% cresol.
E. Treatment: Ciprofloxacin is now a days the drug of choice.
F. Follow-up: Stool and Urine examination should be done for detection of S. typhi, 3 to 4 months after discharge of the patient.
G. Prevention: 1. Community measure: Ensure Safe water supply, ensure safety food, proper disposal of human excreta and garbage, health education. 2. Immunization: a. Ty21a Vaccine(Vivotif Berna, Swiss Serum and Vaccine Institute) 1 capsule by mouth 4 doses @ 2 days alternate b. ViCPS (Typhim Vi, Pasteur Merieux) Injection single dose
TYPHOID IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• Typhoid fever is very common in Bangladesh, where this pathogen thrives in areas where disasters have compromised sanitation with the typical tropic zone.
• Preliminary results from recent studies conducted in Bangladesh by ICDDR,B show an incidence of approximately 2000 per 100 000 per year.
• Typhoid is a curable as well as preventable disease, and socio-economic impact is huge, so it is in consideration and concern of public health.
• Typhoid fever is common in Bangladesh because water supplies and sanitation are sub-standard.
TUBERCULOSIS
Tuberculosis is a chronic infectious and communicable infectious disease caused by Mycobacterium tuberculosis. This disease primarily affects lungs but it may affect other organs also e.g. Intestines, Bones, Joints, Lymph glands and others.
PREVENTION AND CONTROL MEASURES
The control of tuberculosis can be considered at the six levels of prevention:
A. General health promotion: Adequate housing, good nutrition, health education.
B. Active immunization: By BCG (Bacille Calmette Guerin) vaccine at birth in a single dose (0.1 ml) intradermally which is a live attenuated vaccine.
C. Early diagnosis and treatment: 1. Screening- Tuberculin test, Staining of sputum, Chest X-ray. 2. Isolation- Patient should preferably be isolated from young children. 3. Drug treatment: The overall goal for treatment of tuberculosis- a. To cure the individual patient b. To minimize the transmission of Mycobacterium tuberculosis to other persons. The anti tubercular drugs are- Isoniazid, Rifampicin, Pyrazinamide, Ethambutol, and Streptomycin. • Regimen for new smear-positive patients and other severely ill patients: 2HRZE/4H3R3 • Regimen for relapses and failures: 2SHRZE/1REHZ/5R3E3H3 • Regimen for smear-negative and extra-pulmonary patients: 2HRZ/4H3R3
D. Rehabilitation
E. Surveillance: The source of data will include- Notification of cases, post mortem reports, record of BCG immunization, housing- data about overcrowding. F. Control strategy: Tuberculosis control means reduction in the prevalence and incidence of disease in the community. DOTS is a control strategy which ensures - • Sustained Political Commitment • Case Detection through Quality assured Sputum microscopy • Uninterrupted supply of Drugs • Standardized treatment regimen • Standardized recording and reporting system
TUBERCULOSIS IS A PUBLIC HEALTH PROBLEM IN BANGLADESH
• Tuberculosis is a major public health problem in Bangladesh. In 2006, World Health Organization (WHO) ranked Bangladesh 6th among the world's 22 high-burden TB countries.
• In Bangladesh, More than 319,000 new cases, including 143,000 sputum smear-positive (SS+) pulmonary TB cases and 70,000 TB-related deaths occur annually.
• WHO declared TB as a global emergency and recommended DOTS strategy. Bangladesh introduced this strategy in 1993 and it is expanded all upazilas by 1998.
Sample Size and its Determination
Sample Size Determination
In sampling analysis the most ticklish questions: What should be the size of the sample or how large or small should be (‘n’)? If the sample size (‘n’) is too small, it may not serve to achieve the objectives and if it is too large, we may incur huge cost and waste resources. As a general rule, one can say that the sample must be of an optimum size I.e. it should neither be excessively large nor too small. Technically, the sample size should be large enough to give a confidence interval of desired width and as such the size of the sample must be chosen by some logical process before sample is taken from the universe. Size of the sample should be determined by researcher keeping in view the following points:
(i) Nature of universe:
Universe may be either homogenous or heterogeneous in nature. If the items of the universe are homogenous, a small sample can serve the purpose. But if the items are heterogeneous, a large sample would be required. Technically, this can be termed as the dispersion factor.
(ii) Number of classes proposed:
If many class-groups (groups and sub-groups) are to be formed, a large sample would be required because a small sample might not be able to give a reasonable number of items in each class-group.
(iii)Nature of study:
If items are to be intensively and continuously studied, the sample should be small. For a general survey the size of the sample should be large, but a small sample 9s considered appropriate in technical survey.
(iv)Type of sampling:
Sampling technique plays an important part in determining the size of the sample. A small random sample is apt to be much superior to a larger but badly selected sample.
(v) Standard of accuracy and acceptable confidence level:
If the standard of accuracy or the level of precision is to be kept high, we shall require relatively larger sample. For doubling the accuracy for a fixed significance level, the sample size has to be increased fourfold.
(vi) Availability of finance:
In practice, size of the sample depends upon the amount of money available for the study purposes. This factor should be kept in view while determining the the size of sample for large samples result in increasing the cost of sampling estimates.
(vii) Other considerations:
Nature of units, size of the population, size of questionnaire, availability of trained investigators, the conditions under which the sample is being conducted, the time available for completion of the study are a few other considerations to which a researcher must pay attention while selecting the size of the sample.
There are two alternative approaches for determining the size of the sample. The first approach is “ to specify the precision of estimation desired and then to determine the sample size necessary to insure it” and the second approach “uses Bayesian statistics to weigh the cost of additional information against the expected value of the additional information”. The first approach is capable of giving a mathematical solution, and as such is a frequently used technique of determining ‘n’. The limitation of this technique is that it does not analyze the sot of gathering information vis-à-vis the expected value of information. The second approach is theoretically optimal, but it is seldom used because of the difficulty involved in measuring the value of information. Hence, we shall mainly concentrate here on the first approach.
Health And Disease
Health
• Health is a state of complete physical, mental, social and spiritual well-being and not merely the absence of disease or infirmity in all matter.
• Spiritual - quality of courage, vigor, liveliness
• Vigor - Mental or physical energy
• Infirmity - Weakness.
• From the definition of health the following dimensions can be inferred:
• Dictionary meaning of Disease is ‘no comfort’; dis means ‘away from’; ease means comfort; therefore, disease means away from comfort, or no comfort. In other words, disease is the general term for deviation from health. Therefore, disease is a condition or state of health where there is a chance that the body and mind may function abnormally. Dr. Badrul Alam (2001) states in his article, ‘Better use of medicine’ that disorder of ease abbreviates itself into the word” disease” and when that uneasiness of self compels the person to behave abnormally he feels he is sick. When the signs and symptoms are manifested and the person seeks the help of the doctors he diagnoses him as a sick person and labels his disease condition. He further adds that medicine and disease should have a close relation. Like disease, medicine can cause disorders in the body economy such as untoward symptoms, side effects, abnormal reactions etc. This is why medicine is to be used to kill disease.
• “Metaphorically speaking, disease is resistance.
• Disease manifested by symptoms, expresses the vital reaction and resistance of the living organism to the inroads of some injurious agent for influence. It is a battle, a struggle, a costly and painfully resistance to an invader
• Health is a state of complete physical, mental, social and spiritual well-being and not merely the absence of disease or infirmity in all matter.
• Spiritual - quality of courage, vigor, liveliness
• Vigor - Mental or physical energy
• Infirmity - Weakness.
• From the definition of health the following dimensions can be inferred:
- Freedom from pain-and a physical sense of well being.
- Freedom from extremes of emotion- and a sense of dynamic calmness.
- Freedom from confusion- and a sense of mental clarity.
- A sense of being part of the whole cosmos; a spiritual sense of purpose in life and a feeling of inner fulfillment.
- Equilibrium and adaptability and ease on all levels (Hence, the word disease) and hence “glowing and flowing”.
- Fully functioning-according to one’s ability
- Living life to the full-according to one’s unique gifts.
- In summary, health is the physiological condition of a person. Any deviation from this physiology may be termed as disease condition or pathology.
• Dictionary meaning of Disease is ‘no comfort’; dis means ‘away from’; ease means comfort; therefore, disease means away from comfort, or no comfort. In other words, disease is the general term for deviation from health. Therefore, disease is a condition or state of health where there is a chance that the body and mind may function abnormally. Dr. Badrul Alam (2001) states in his article, ‘Better use of medicine’ that disorder of ease abbreviates itself into the word” disease” and when that uneasiness of self compels the person to behave abnormally he feels he is sick. When the signs and symptoms are manifested and the person seeks the help of the doctors he diagnoses him as a sick person and labels his disease condition. He further adds that medicine and disease should have a close relation. Like disease, medicine can cause disorders in the body economy such as untoward symptoms, side effects, abnormal reactions etc. This is why medicine is to be used to kill disease.
• “Metaphorically speaking, disease is resistance.
• Disease manifested by symptoms, expresses the vital reaction and resistance of the living organism to the inroads of some injurious agent for influence. It is a battle, a struggle, a costly and painfully resistance to an invader
BURNING ISSUES OF PUBLIC HEALTH IN BANGLADESH
Bangladesh is a densely populated country. Masses of people in Bangladesh face a perilous situation due to hazardous health conditions in the country. The main source of these conditions is the poverty and backwardness maintained and deepened by capitalist rule. As a result serious health problems became a burden to this country. Major health problems, which became concerning issues for the public health management of this country, are given below-
PUBLIC HEALTH HAZARDS IN BANGLADESH-
• COMMUNICABLE DISEASE PROBLEM-
Malaria, Filariasis, TB, Leprosy, Diarrhoel Disease, Cholera, Acute Respiratory Infection (ARI), Acquired Immune Deficiency Syndrome (AIDS)
• NUTRIONAL PROBLEMS-
Protein Energy Malnutrition (PEM), Low Birth Weight, Nutritional Anemia (Iron deficiency), Nutritional Blindness (Xeropthalamia), Iodine Deficiency Disorder (IDD), Neurolathyrism, Endemic Flurosis.
• ENVIRONMENTAL SANITATION PROBLEM-
Lack of safe water supply, Lack of sanitary disposal of refuse, Sewage &
Excreta, Noise & air pollution, Lack of quality good food & consumer
Products.
• MEDICAL CARE PROBLEM-
Inadequate financial resources, health manpower and health infrastructure, uneven distribution of health personnel/doctors, more in urban areas, overcrowding in hospitals due to migration from rural to urban.
• POPULATION PROBLEM-
This is related to all aspects of development especially in Employment,
Education, Environment, Housing, Health care, Sanitation, Family planning.
Population explosion.
• SOCIAL PROBLEMS –
Alcoholism, Drug dependence, Sexually transmitted disease, Prostitution, Dowry system.
PUBLIC HEALTH HAZARDS IN BANGLADESH-
• COMMUNICABLE DISEASE PROBLEM-
Malaria, Filariasis, TB, Leprosy, Diarrhoel Disease, Cholera, Acute Respiratory Infection (ARI), Acquired Immune Deficiency Syndrome (AIDS)
• NUTRIONAL PROBLEMS-
Protein Energy Malnutrition (PEM), Low Birth Weight, Nutritional Anemia (Iron deficiency), Nutritional Blindness (Xeropthalamia), Iodine Deficiency Disorder (IDD), Neurolathyrism, Endemic Flurosis.
• ENVIRONMENTAL SANITATION PROBLEM-
Lack of safe water supply, Lack of sanitary disposal of refuse, Sewage &
Excreta, Noise & air pollution, Lack of quality good food & consumer
Products.
• MEDICAL CARE PROBLEM-
Inadequate financial resources, health manpower and health infrastructure, uneven distribution of health personnel/doctors, more in urban areas, overcrowding in hospitals due to migration from rural to urban.
• POPULATION PROBLEM-
This is related to all aspects of development especially in Employment,
Education, Environment, Housing, Health care, Sanitation, Family planning.
Population explosion.
• SOCIAL PROBLEMS –
Alcoholism, Drug dependence, Sexually transmitted disease, Prostitution, Dowry system.
BIAS AND CONFOUNDING
HYPOTHESIS FORMULATION AND ERRORS IN RESEARCH
All analytic studies must begin with a clearly formulated hypothesis. The hypothesis must be quantitative and specific. It must predict a relationship of a specific size.
For example:
“Babies who are breast-fed have less illness than babies who are bottle-fed.”
Which illnesses? How is feeding type defined? How large a difference in risk?
A better example:
“Babies who are exclusively breast-fed for three months or more will have a reduction in the incidence of hospital admissions for gastroenteritis of at least 30% over the first year of life.”
Only specific prediction allows one to draw legitimate conclusions from a study which tests a hypothesis. But even with the best formulated hypothesis, two types of errors can occur.
• Type 1 - observing a difference when in truth there is none.
• Type 2 - failing to observe a difference when there is one.
These errors are generally produced by one or more of the following:
• RANDOM ERROR
• RANDOM MISCLASSIFICATION
• BIAS
• CONFOUNDING
RANDOM ERROR :
Deviation of results and inferences from the truth, occurring only as a result of the operation of chance. Can produce type 1 or type 2 errors.
RANDOM (OR NON-DIFFERENTIAL) MISCLASSIFICATION :
Random error applied to the measurement of an exposure or outcome. Errors in classification can only produce type 2 errors, except if applied to a confounder or to an exposure gradient.
BIAS:
Systematic, non-random deviation of results and inferences from the truth, or processes leading to such deviation. Any trend in the collection, analysis, interpretation, publication or review of data that can lead to conclusions which are systematically different from the truth.
Note that in bias, the focus is on an artifact of some part of the research process (assembling subjects, collecting data, analyzing data) that produces a spurious result. Bias can produce either a type 1 or a type 2 error, but we usually focus on type 1 errors due to bias.
Bias can be either conscious or unconscious. In epidemiology, the word bias does not imply, as in common usage, prejudice or deliberate deviation from the truth.
CONFOUNDING :
A problem resulting from the fact that one feature of study subjects has not been separated from a second feature, and has thus been confounded with it, producing a spurious result. The spuriousness arises from the effect of the first feature being mistakenly attributed to the second feature. Confounding can produce either a type 1 or a type 2 error, but we usually focus on type 1 errors.
THE DIFFERENCE BETWEEN BIAS AND CONFOUNDING:
Bias creates an association that is not true, but confounding describes an association that is true, but potentially misleading.
EXAMPLES OF RANDOM ERROR, BIAS, MISCLASSIFICATION AND CONFOUNDING IN THE SAME STUDY:
STUDY: In a cohort study, babies of women who bottle feed and women who breast feed are compared, and it is found that the incidence of gastroenteritis, as recorded in medical records, is lower in the babies who are breast-fed.
EXAMPLE OF RANDOM ERROR :
By chance, there are more episodes of gastroenteritis in the bottle-fed group in the study sample, producing a type 1 error. (When in truth breast feeding is not protective against gastroenteritis).
Or, also by chance, no difference in risk was found, producing a type 2 error (When in truth breast feeding is protective against gastroenteritis).
EXAMPLE OF RANDOM MISCLASSIFICATION :
Lack of good information on feeding history results in some breast-feeding mothers being randomly classified as bottle-feeding, and vice-versa. If this happens, the study finding underestimates the true RR, whichever feeding modality is associated with higher disease incidence, producing a type 2 error.
EXAMPLE OF BIAS:
The medical records of bottle-fed babies only are less complete (perhaps bottle fed babies go to the doctor less) than those of breast fed babies, and thus record fewer episodes of gastro-enteritis in them only.
This is called ias because the observation itself is in error.
EXAMPLE OF CONFOUNDING :
The mothers of breast-fed babies are of higher social class, and the babies thus have better hygiene, less crowding and perhaps other factors that protect against gastroenteritis. Crowding and hygiene are truly protective against gastroenteritis, but we mistakenly attribute their effects to breast feeding. This is called confounding. because the observation is correct, but its explanation is wrong.
PROTECTION AGAINST RANDOM ERROR AND RANDOM MISCLASSIFICATION:
Random error can work to falsely produce an association (type 1 error) or falsely not produce an association (type 2 error).
We protect ourselves against random misclassification producing a type 2 error by choosing the most precise and accurate measures of exposure and outcome.
PROTECTION AGAINST TYPE 1 ERRORS:
We protect our study against random type 1 errors by establishing that the result must be unlikely to have occurred by chance (e.g. p < .05). P-values are established entirely to protect against type 1 errors due to chance, and do not guarantee protection against type 1 errors due to bias or confounding. This is the reason we say statistics demonstrate association but not causation. PROTECTION AGAINST TYPE 2 ERRORS: We protect our study against random type 2 errors by providing adequate sample size, and hypothesizing large differences. The larger the sample size, the easier it will be to detect a true difference, and the largest differences will be the easiest to detect. (Imagine how hard it would be to detect a 1% increase in the risk of gastroenteritis with bottle-feeding). TWO WAYS TO INCREASE POWER: The sample size needed to detect a significant difference is called the power of a study. 1.Choosing the most precise and accurate measures of exposure and outcome has the effect of increasing the power of our study, because of variances of the outcome measures, which enter into statistical testing, are decreased. 2.Having an adequate sized sample of study subjects KEY PRINCIPLE IN BIAS AND CONFOUNDING :
The factor that creates the bias, or the confounding variable, must be associated with both the independent and dependent variables (i.e. with the exposure and the disease). Association of the bias or confounder with just one of the two variables is not enough to produce a spurious result.
In the example just given:
The BIAS, namely incomplete chart recording, has to be associated with feeding type (the independent variable) and also with recording of gastroenteritis (the dependent variable) to produce the false result.
The CONFOUNDING VARIABLE (or CONFOUNDER) better hygiene, has to be associated with feeding type and also with gastroenteritis to produce the spurious result.
Were the bias or the confounder associated with just the independent variable or just the dependent variable, they would not produce bias or confounding.
This gives a useful rule:
If you can show that a potential confounder is NOT associated with either one of the two variables under study (exposure or outcome), confounding can be ruled out.
SOME TYPES OF BIAS:
1. SELECTION BIAS
Any aspect of the way subjects are assembled in the study that creates a systematic difference between the compared populations that is not due to the association under study.
2. INFORMATION BIAS
Any aspect of the way information is collected in the study that creates a systematic difference between the compared populations that is not due to the association under study. (some call this measurement bias). The incomplete chart recording in the baby feeding example would be a form of information bias.
Other examples -
Diagnostic suspicion bias
Recall bias
Sometimes biases apply to a population of studies, rather than to one study, as in publication bias (tendency to publish papers which show positive results).
All analytic studies must begin with a clearly formulated hypothesis. The hypothesis must be quantitative and specific. It must predict a relationship of a specific size.
For example:
“Babies who are breast-fed have less illness than babies who are bottle-fed.”
Which illnesses? How is feeding type defined? How large a difference in risk?
A better example:
“Babies who are exclusively breast-fed for three months or more will have a reduction in the incidence of hospital admissions for gastroenteritis of at least 30% over the first year of life.”
Only specific prediction allows one to draw legitimate conclusions from a study which tests a hypothesis. But even with the best formulated hypothesis, two types of errors can occur.
• Type 1 - observing a difference when in truth there is none.
• Type 2 - failing to observe a difference when there is one.
These errors are generally produced by one or more of the following:
• RANDOM ERROR
• RANDOM MISCLASSIFICATION
• BIAS
• CONFOUNDING
RANDOM ERROR :
Deviation of results and inferences from the truth, occurring only as a result of the operation of chance. Can produce type 1 or type 2 errors.
RANDOM (OR NON-DIFFERENTIAL) MISCLASSIFICATION :
Random error applied to the measurement of an exposure or outcome. Errors in classification can only produce type 2 errors, except if applied to a confounder or to an exposure gradient.
BIAS:
Systematic, non-random deviation of results and inferences from the truth, or processes leading to such deviation. Any trend in the collection, analysis, interpretation, publication or review of data that can lead to conclusions which are systematically different from the truth.
Note that in bias, the focus is on an artifact of some part of the research process (assembling subjects, collecting data, analyzing data) that produces a spurious result. Bias can produce either a type 1 or a type 2 error, but we usually focus on type 1 errors due to bias.
Bias can be either conscious or unconscious. In epidemiology, the word bias does not imply, as in common usage, prejudice or deliberate deviation from the truth.
CONFOUNDING :
A problem resulting from the fact that one feature of study subjects has not been separated from a second feature, and has thus been confounded with it, producing a spurious result. The spuriousness arises from the effect of the first feature being mistakenly attributed to the second feature. Confounding can produce either a type 1 or a type 2 error, but we usually focus on type 1 errors.
THE DIFFERENCE BETWEEN BIAS AND CONFOUNDING:
Bias creates an association that is not true, but confounding describes an association that is true, but potentially misleading.
EXAMPLES OF RANDOM ERROR, BIAS, MISCLASSIFICATION AND CONFOUNDING IN THE SAME STUDY:
STUDY: In a cohort study, babies of women who bottle feed and women who breast feed are compared, and it is found that the incidence of gastroenteritis, as recorded in medical records, is lower in the babies who are breast-fed.
EXAMPLE OF RANDOM ERROR :
By chance, there are more episodes of gastroenteritis in the bottle-fed group in the study sample, producing a type 1 error. (When in truth breast feeding is not protective against gastroenteritis).
Or, also by chance, no difference in risk was found, producing a type 2 error (When in truth breast feeding is protective against gastroenteritis).
EXAMPLE OF RANDOM MISCLASSIFICATION :
Lack of good information on feeding history results in some breast-feeding mothers being randomly classified as bottle-feeding, and vice-versa. If this happens, the study finding underestimates the true RR, whichever feeding modality is associated with higher disease incidence, producing a type 2 error.
EXAMPLE OF BIAS:
The medical records of bottle-fed babies only are less complete (perhaps bottle fed babies go to the doctor less) than those of breast fed babies, and thus record fewer episodes of gastro-enteritis in them only.
This is called ias because the observation itself is in error.
EXAMPLE OF CONFOUNDING :
The mothers of breast-fed babies are of higher social class, and the babies thus have better hygiene, less crowding and perhaps other factors that protect against gastroenteritis. Crowding and hygiene are truly protective against gastroenteritis, but we mistakenly attribute their effects to breast feeding. This is called confounding. because the observation is correct, but its explanation is wrong.
PROTECTION AGAINST RANDOM ERROR AND RANDOM MISCLASSIFICATION:
Random error can work to falsely produce an association (type 1 error) or falsely not produce an association (type 2 error).
We protect ourselves against random misclassification producing a type 2 error by choosing the most precise and accurate measures of exposure and outcome.
PROTECTION AGAINST TYPE 1 ERRORS:
We protect our study against random type 1 errors by establishing that the result must be unlikely to have occurred by chance (e.g. p < .05). P-values are established entirely to protect against type 1 errors due to chance, and do not guarantee protection against type 1 errors due to bias or confounding. This is the reason we say statistics demonstrate association but not causation. PROTECTION AGAINST TYPE 2 ERRORS: We protect our study against random type 2 errors by providing adequate sample size, and hypothesizing large differences. The larger the sample size, the easier it will be to detect a true difference, and the largest differences will be the easiest to detect. (Imagine how hard it would be to detect a 1% increase in the risk of gastroenteritis with bottle-feeding). TWO WAYS TO INCREASE POWER: The sample size needed to detect a significant difference is called the power of a study. 1.Choosing the most precise and accurate measures of exposure and outcome has the effect of increasing the power of our study, because of variances of the outcome measures, which enter into statistical testing, are decreased. 2.Having an adequate sized sample of study subjects KEY PRINCIPLE IN BIAS AND CONFOUNDING :
The factor that creates the bias, or the confounding variable, must be associated with both the independent and dependent variables (i.e. with the exposure and the disease). Association of the bias or confounder with just one of the two variables is not enough to produce a spurious result.
In the example just given:
The BIAS, namely incomplete chart recording, has to be associated with feeding type (the independent variable) and also with recording of gastroenteritis (the dependent variable) to produce the false result.
The CONFOUNDING VARIABLE (or CONFOUNDER) better hygiene, has to be associated with feeding type and also with gastroenteritis to produce the spurious result.
Were the bias or the confounder associated with just the independent variable or just the dependent variable, they would not produce bias or confounding.
This gives a useful rule:
If you can show that a potential confounder is NOT associated with either one of the two variables under study (exposure or outcome), confounding can be ruled out.
SOME TYPES OF BIAS:
1. SELECTION BIAS
Any aspect of the way subjects are assembled in the study that creates a systematic difference between the compared populations that is not due to the association under study.
2. INFORMATION BIAS
Any aspect of the way information is collected in the study that creates a systematic difference between the compared populations that is not due to the association under study. (some call this measurement bias). The incomplete chart recording in the baby feeding example would be a form of information bias.
Other examples -
Diagnostic suspicion bias
Recall bias
Sometimes biases apply to a population of studies, rather than to one study, as in publication bias (tendency to publish papers which show positive results).
WHO Theme 2007 - ‘Invest in health, build a safer future’
The 2007, World Health Day slogan ‘Invest in health, build a safer future’ addresses one of the most vital concerns of out times. Globalization, rapid travel and trade make it much easier for new and existing diseases to leap over national borders and threaten our collective security.
Avian Influenza in 2006 and SARS in 2003 spread from one country and region to the next. HIV/AIDS is also racing across nations, adversely impacting their economies and threatening their stability. New diseases have appeared and old ones have re-emerged as epidemic/pandemic prone diseases to present an acute threat to life. Climate change, natural disasters, chemical and nuclear accidents and bioterrorism also hold the potential to threaten international public health security. When health emergencies give rise to global concerns, an effective response requires international coordination as has been seen post tsunami and the SARS outbreak. The WHO slogan highlights the crucial need to invest in human resources and strengthened health systems to enable the international community to effectively meet the public health risks and challenges.
WHO is assisting countries to strengthen their public health capabilities. The revised and broadened International Health Regulations (2005) which will come into force in June 2007 will provide an important instrument to protect countries from global health destabilization. Under this international agreement, WHO Member States are obliged to prevent and control the spread of disease inside and outside their borders. They are required to maintain core surveillance and response capacities to detect, assess, notify and report public health events to WHO and to respond to public health risks and public health emergencies.
A concept for World Health Day 2007 is to Invest in health, build a safer future.
The goal of World Health Day 2007 is to focus on international health security issues, to engage high-level political interest in addressing these issues, and to show the close link of health to national and international security agendas. Over the past few decades, the concept of security was redefined to reflect a shift from the national security as a state-centered defense strategy, to the belief that human security is centered on the people. This new concept of security addresses socioeconomic, natural and man-made threats that jeopardize people’s own development and rights. The UNDP’s (1994) Human Development Report, New Dimensions of Human Security reports on these types of threats that affect people. Among these, health security is defined as guaranteeing minimum protection from disease and unhealthy lifestyles, along with food, environmental, economic, community and political security.
Global health security serves as one of the World Health Organization's (WHO) priorities as public health systems worldwide are repeatedly challenged by naturally occurring emerging and re-emerging diseases, environmental changes, natural disasters, and accidental or intentional release of different agents which may constitute public health emergencies. The aim now is to strengthen our commitment to reduce threats to human lives and health inequities and to guarantee the right to live with dignity.
According to the WHO, the theme of World Health Day and the World Health Report 2007 is to show that in a Globalized World, health issues increasingly present new challenges that go far beyond a national border and that have impact on the collective security of all people. Increased collaboration among all people and nations will better enable the international community to work for better health and in turn assist in making the world more secure.
While there are many aspects of international health security that should be addressed, the main focus of the Pan American Health Organization (PAHO) will concentrate on the following issues:
1. Emerging and Reemerging Infectious Diseases
2. International Health Regulations {IHR ( 2005)}
3. Public Health Infrastructure
4. Promoting Health Security through Sustainable Development in Healthy Settings
1. Emerging and Reemerging Infectious Diseases
Throughout history, epidemics of infectious diseases took their toll on human lives and often resulted in social disruption, political instability, barriers to trade and travel and had tremendous economic and social consequences. In the past three decades alone, new pathogens and diseases emerged as killers such as HIV/AIDS in the mid 1980s, dengue hemorrhagic fever in 1981 in the Americas, the reemergence of cholera in 1991 after an absence of more than a century, antivirus pulmonary syndrome in 1993, West Nile virus encephalitis in 1999 and severe acute respiratory syndrome (SARS) in 2003. Most of these diseases are caused mainly by environmental, ecological or demographic factors which are spread worldwide by travel and trade. This spread of disease can be attributed to human behavior and population movements, which poses risks to global health security. The emergence of a new subtype of the influenza virus that initially infected animals and subsequently infected humans highlights the precarious stability of nations’ socioeconomic conditions.
2. International Health Regulations [IHR ( 2005)]
Recognizing the link between the globalization of trade and travel and the spread of infectious diseases, WHO began identifying, verifying and responding to public health emergencies of international concern. The legal framework is the recently adopted International Health Regulations (2005), which seek to "prevent, protect against, control and provide a public health response to the international spread of disease in ways that are commensurate with and restricted to public health risks, and which avoid unnecessary interference with international traffic and trade." Scheduled to enter into force in June 2007, the IHR (2005) represents a major step for international cooperation and action in the fight against the spread of epidemics.
Countries bound by the IHR (2005) need to develop, strengthen and maintain their capacity to detect, report and respond to public health events and to provide routine inspection and health control activities at international airports, ports, and some ground crossings. The investment required to build a safer future is the responsibility of the health sector in partnership with other sectors (agriculture, defense, transportation, tourism etc.) as well as by the community at large.
3. Public Health Infrastructure
Public health emergencies highlight the strengths and weaknesses of the public health infrastructure that is designed to protect the population. Detecting and responding to a public health emergency involves all essential public health activities, including surveillance, health care services, laboratory capacity, human resources, and communication between various actors and the general public. Resources from an inter-sectoral and inter-institutional alliance are required in today’s inter-dependent -world, where a local epidemic event can rapidly turn into a global event and economic threat.
For example, the international response to the SARS outbreak was an extreme test of public health systems. WHO’s success in coordinating the containment of this previously unknown disease was mainly due to the detection and response mechanisms already in place.
4. Promoting Health Security through Sustainable Development in Healthy
Settings
Natural and man-made disasters, such as hurricanes, earthquakes, tsunamis, chemical and nuclear spills, bioterrorism and large outbreaks of new and re-emerging infectious diseases are receiving increasing attention in a shared international public health agenda. In a Globalized World, large scale disasters not only result in a large loss of lives but often lead to a collective sense of vulnerability and insecurity in communities. The public health of the 21st Century embraces the multidimensional nature of new challenges to international health security. The new focus on social determinants is a reflection of the effects on the environment and inequities for human development in a global economy.
International health security requires a larger and more effective interaction between countries, governments, institutions, communities, and citizens. All sectors of society and all citizens share responsibility for health security. Renewed efforts in building basic public health infrastructure and preparation serve as key to the response, and the better prepared a society is as a whole, the more organized and effective the response. In addressing public health threats of international concern, it is important to acknowledge the complexities of promoting and maintaining health security. Therefore it is fundamental to advocate for long term investment in healthy policies which involved the public and private sector at all levels, as well as concerted action with local governments, civil institutions, health services and the communities they serve.
Therefore, considering the WHO Theme ‘Invest in health, build a safer future’, this investment will provide both better health security and improved opportunities for human development in places where people live, learn, and work.
Avian Influenza in 2006 and SARS in 2003 spread from one country and region to the next. HIV/AIDS is also racing across nations, adversely impacting their economies and threatening their stability. New diseases have appeared and old ones have re-emerged as epidemic/pandemic prone diseases to present an acute threat to life. Climate change, natural disasters, chemical and nuclear accidents and bioterrorism also hold the potential to threaten international public health security. When health emergencies give rise to global concerns, an effective response requires international coordination as has been seen post tsunami and the SARS outbreak. The WHO slogan highlights the crucial need to invest in human resources and strengthened health systems to enable the international community to effectively meet the public health risks and challenges.
WHO is assisting countries to strengthen their public health capabilities. The revised and broadened International Health Regulations (2005) which will come into force in June 2007 will provide an important instrument to protect countries from global health destabilization. Under this international agreement, WHO Member States are obliged to prevent and control the spread of disease inside and outside their borders. They are required to maintain core surveillance and response capacities to detect, assess, notify and report public health events to WHO and to respond to public health risks and public health emergencies.
A concept for World Health Day 2007 is to Invest in health, build a safer future.
The goal of World Health Day 2007 is to focus on international health security issues, to engage high-level political interest in addressing these issues, and to show the close link of health to national and international security agendas. Over the past few decades, the concept of security was redefined to reflect a shift from the national security as a state-centered defense strategy, to the belief that human security is centered on the people. This new concept of security addresses socioeconomic, natural and man-made threats that jeopardize people’s own development and rights. The UNDP’s (1994) Human Development Report, New Dimensions of Human Security reports on these types of threats that affect people. Among these, health security is defined as guaranteeing minimum protection from disease and unhealthy lifestyles, along with food, environmental, economic, community and political security.
Global health security serves as one of the World Health Organization's (WHO) priorities as public health systems worldwide are repeatedly challenged by naturally occurring emerging and re-emerging diseases, environmental changes, natural disasters, and accidental or intentional release of different agents which may constitute public health emergencies. The aim now is to strengthen our commitment to reduce threats to human lives and health inequities and to guarantee the right to live with dignity.
According to the WHO, the theme of World Health Day and the World Health Report 2007 is to show that in a Globalized World, health issues increasingly present new challenges that go far beyond a national border and that have impact on the collective security of all people. Increased collaboration among all people and nations will better enable the international community to work for better health and in turn assist in making the world more secure.
While there are many aspects of international health security that should be addressed, the main focus of the Pan American Health Organization (PAHO) will concentrate on the following issues:
1. Emerging and Reemerging Infectious Diseases
2. International Health Regulations {IHR ( 2005)}
3. Public Health Infrastructure
4. Promoting Health Security through Sustainable Development in Healthy Settings
1. Emerging and Reemerging Infectious Diseases
Throughout history, epidemics of infectious diseases took their toll on human lives and often resulted in social disruption, political instability, barriers to trade and travel and had tremendous economic and social consequences. In the past three decades alone, new pathogens and diseases emerged as killers such as HIV/AIDS in the mid 1980s, dengue hemorrhagic fever in 1981 in the Americas, the reemergence of cholera in 1991 after an absence of more than a century, antivirus pulmonary syndrome in 1993, West Nile virus encephalitis in 1999 and severe acute respiratory syndrome (SARS) in 2003. Most of these diseases are caused mainly by environmental, ecological or demographic factors which are spread worldwide by travel and trade. This spread of disease can be attributed to human behavior and population movements, which poses risks to global health security. The emergence of a new subtype of the influenza virus that initially infected animals and subsequently infected humans highlights the precarious stability of nations’ socioeconomic conditions.
2. International Health Regulations [IHR ( 2005)]
Recognizing the link between the globalization of trade and travel and the spread of infectious diseases, WHO began identifying, verifying and responding to public health emergencies of international concern. The legal framework is the recently adopted International Health Regulations (2005), which seek to "prevent, protect against, control and provide a public health response to the international spread of disease in ways that are commensurate with and restricted to public health risks, and which avoid unnecessary interference with international traffic and trade." Scheduled to enter into force in June 2007, the IHR (2005) represents a major step for international cooperation and action in the fight against the spread of epidemics.
Countries bound by the IHR (2005) need to develop, strengthen and maintain their capacity to detect, report and respond to public health events and to provide routine inspection and health control activities at international airports, ports, and some ground crossings. The investment required to build a safer future is the responsibility of the health sector in partnership with other sectors (agriculture, defense, transportation, tourism etc.) as well as by the community at large.
3. Public Health Infrastructure
Public health emergencies highlight the strengths and weaknesses of the public health infrastructure that is designed to protect the population. Detecting and responding to a public health emergency involves all essential public health activities, including surveillance, health care services, laboratory capacity, human resources, and communication between various actors and the general public. Resources from an inter-sectoral and inter-institutional alliance are required in today’s inter-dependent -world, where a local epidemic event can rapidly turn into a global event and economic threat.
For example, the international response to the SARS outbreak was an extreme test of public health systems. WHO’s success in coordinating the containment of this previously unknown disease was mainly due to the detection and response mechanisms already in place.
4. Promoting Health Security through Sustainable Development in Healthy
Settings
Natural and man-made disasters, such as hurricanes, earthquakes, tsunamis, chemical and nuclear spills, bioterrorism and large outbreaks of new and re-emerging infectious diseases are receiving increasing attention in a shared international public health agenda. In a Globalized World, large scale disasters not only result in a large loss of lives but often lead to a collective sense of vulnerability and insecurity in communities. The public health of the 21st Century embraces the multidimensional nature of new challenges to international health security. The new focus on social determinants is a reflection of the effects on the environment and inequities for human development in a global economy.
International health security requires a larger and more effective interaction between countries, governments, institutions, communities, and citizens. All sectors of society and all citizens share responsibility for health security. Renewed efforts in building basic public health infrastructure and preparation serve as key to the response, and the better prepared a society is as a whole, the more organized and effective the response. In addressing public health threats of international concern, it is important to acknowledge the complexities of promoting and maintaining health security. Therefore it is fundamental to advocate for long term investment in healthy policies which involved the public and private sector at all levels, as well as concerted action with local governments, civil institutions, health services and the communities they serve.
Therefore, considering the WHO Theme ‘Invest in health, build a safer future’, this investment will provide both better health security and improved opportunities for human development in places where people live, learn, and work.
Descriptive Studies: Design, Conduction and Analysis
Epidemiology is concerned with the study of distribution and determinant of disease or any health related problem in the community. Epidemiological studies can be classified as
1. Descriptive studies: In descriptive studies, the pattern of disease occurrence is described in terms of time, place and person. Descriptive studies utilise information from diverse sources of data such as census, vital statistical records, hospital records as well as national figures about consumption of food, medications and other products. Descriptive studies are conducted especially to understand the disease pattern, extent of the problem and to generate research questions and hypothesis. Descriptive studies are generally less expensive and time-consuming than the analytic studies. Types of descriptive studies are
a. Case reports and case series
b. Correlational study
c. Cross-sectional study
2. Analytic studies: are conducted to identify the risk factor(s) for diseases or evaluate the interventions for control of disease(s) or other health problems. The analytic studies include:
a. Observational studies: such as, case-control and cohort studies
b. Experimental: such as, intervention trials (clinical trial and community trial)
1.1 Case report and case series:
Case reports and case series are the most frequently published articles in the medical journals. Case reports and case series usually describe the experience of a single patient (case report) or a group of patients (case series) with a similar disease. Case report documents unusual medical occurrences and can represent the first clues in the identification of new disease or adverse effects of medications (e.g., emergence of new disease like AIDS, thalidomide tragedy and use of oral contraceptive and development of venous thrombosis etc.). Case series are collections of individual case reports, which may occur, in fairly a short period of time. Such studies are important especially to identify the beginning or presence of an epidemic in the community. These types of studies where there are unusual features of disease (or patient’s history) may lead into generation of hypothesis. Although such studies provide important clues for generation of hypothesis, they cannot be tested because of lack of an appropriate comparison group. It is therefore necessary to design an appropriate analytic study to identify the possible factor.
1.2 Correlational study:
Also called ecological study. In this study design, the investigator collects or uses information from a community (or country) as whole rather than from individuals and search for associations among various factors present in the community. Main features of such study design are:
- It usually compares mortality or disease prevalence in different groups of people or community or country
- The unit of observation is the entire community (or country)
- The estimated exposure level found in that community or geographical unit is a surrogate measure for exposure of all individuals in that unit
- Linkage between individual exposure and individual suffering for a certain disease (or death) cannot be ascertained
Once information is collected, scatter diagram of morbidity (or mortality) rates against the average exposure rates in each community (or country or geographical areas) is constructed to assess possible association between exposure and outcome of interest. Other measures of association, such as correlation coefficient, coefficient of determination, are also calculated to quantify the relationship between the variables of interest and outcome. Such studies especially help to generate hypothesis between exposure and disease association. For example, to describe the pattern of morbidity of coronary heart disease (CHD) in 1960, death rates from 44 states (in US) were collected with per capita cigarette sales. It was observed that the death rates were highest in states with most cigarette sales, lowest in those with the least sales, and intermediate in the remainder. This observation contributed to the formulation of hypothesis that cigarette smoking causes fatal CHD, which has been documented subsequently in large number of analytic studies.
The advantages of such study is that it utilises the available data from different sources for analysis, thus can be conducted with minimum time and resources. However, the limitations of such studies are a) unable to link exposure with disease among individuals; b) correlational study presents average exposure of values rather than actual individual levels and c) subjected to potential confounding bias, which cannot be controlled during analysis. For example, a correlational study found association between increased pork consumption and breast cancer. Increased pork consumption may merely be a marker for a number of other factors for the increased risk of breast cancer, such as increased dietary fat, decreased vegetable intake or higher socio-economic status of people. It is not possible to separate the effects of such potential confounding factors while analysing data.
1.3 Cross-sectional study:
Also called prevalence survey. Main objective of such study is to describe the pattern of disease prevalence (not incidence) in the community at a certain point in time as well as to test association between possible risk factors with the disease for generation of hypothesis to be tested by analytical studies. Cross sectional study measures the exposure status and disease among the individuals at the same time. In many cases it is therefore not possible to determine whether the exposure preceded or resulted from the disease. For example, a cross sectional study found association between serum retinol (vitamin A) level and colonic cancer. It is very difficult to say from the cross sectional data whether low serum retinol is responsible for development of colonic cancer or it is the consequence, due to change in dietary habits. Such type of dilemma is common virtually in all the cross sectional studies.
Cross-sectional study reflects current status of health of a community. Such study is valuable both to the public health administrator (programme personnel) as well as to the epidemiologist. Cross sectional study findings are utilised by the health planers to understand the health status of the community, extent and distribution of health problems, priority setting, efficient allocation of resources and planning for intervention, while epidemiologist utilise the findings to identify the possible risk factors to design analytical studies to confirm them and provide recommendations on preventive interventions. For example, in Bangladesh Demographic and Health Survey is conducted every two years, collecting information through household interviews from a random sample of the population. It provides valuable information on population, fertility, mortality, nutritional status, child health and maternal health for effective health care planning and administration.
Cross sectional survey can also be utilised to determine the prevalence of disease or other health outcome in a specific group of people, such as in certain occupation. Such survey provides information on occupational exposure and frequency of disease.
1.3.1 Conduction:
Cross sectional survey is usually conducted by taking a sample from the defined population of interest. If the population size is small whole population may be studied provided there is enough resources available for this. To have a representative sample of the population, sample may be selected through either of the methods such as a) simple random sampling; b) systematic sampling; c) stratified random sampling and d) cluster sampling. Once the sample is selected, data are collected from the study subjects through a) questionnaire interview; b) observation; c) physical examination; and d) lab examinations.
1.3.2 Data analysis:
As mentioned earlier, from the cross sectional study we can only calculate the prevalence of disease in the community. Data are analysed mostly in terms of descriptive statistics and presented in the form of table, graphs or charts. We can also find association between the factor(s) of interest and the disease using appropriate statistical methods.
Example:
To determine the prevalence of sputum positive tuberculosis (TB) in a community, a random sample of 400 individuals (age more than 10 years) have been selected who gave history of cough for more than 2 weeks. Morning sputum from all of them was collected and was checked for AFB (acid-fast bacillus). Out of 400 sputum collected, AFB was found in the sputum of 32 individuals. Therefore, prevalence of sputum positive TB in the community is
Prevalence of sputum +ve TB = (32 400) X 100 or 8%
Data of the survey are cross classified by sex and is given in the following table.
AFB in sputum
+Ve -Ve Total
11
(a)
239
(b) 250
(a+b)
Male
21
(c)
129
(d) 150
(b+d)
Female
Total 32 368 400
Now we can compute prevalence rates among males and females as follows:
Prevalence rate among males
= [a (a + b)] X 100,
or, (11 250) X 100 or 4.4%;
Prevalence rate among females = [c (c + d)] X 100,
or (21 150) X 100 or 14.0%
Data clearly indicate that the prevalence of TB is much higher among the females compared to the males. As these (prevalence rates) are not the direct measures of the disease frequency (incidence rates) among males and females, we cannot really compute the relative risk. However, we can find association between TB and sex by using the Chi-square test, formula for which is as follows:
2 = [n (ad – bc)2] [(a + b) (c + d) (a + c) (b + d)]
In our example, 2 = 11.7, which is much higher than the tabulated value (3.841 with df 1). Therefore, we can say that there is association between sex and sputum positive TB in the community.
In the same manner, association between other factor(s) of interest and TB can be determined.
1.3.3 Advantages and disadvantages of cross-sectional studies:
Advantages:
- Can be conducted quickly and easily with limited resources.
- Provides possible means to find association between possible risk factors and disease without question of temporality, particularly for the permanent characteristics of the individuals (e.g., sex, race, blood group etc.).
Disadvantages:
- Only provides information about disease prevalence but not the incidence of disease in the community
- It provides “snapshot” information about the community at a specific point in time
- In most instances, causal relationship between a factor and disease cannot be determined
- It requires well planned sampling scheme to generalise the findings
- There are also problem of non-response for such kind of study design
3. Hypothesis formulation from descriptive studies:
For any public health problem, first step in the search for possible solutions is to formulate a reasonable and testable hypothesis. There are three methods of hypothesis formulation about disease aetiology as described below.
a. Method of difference: involves reasoning that disease frequency is different in two sets of circumstances. If frequency of a disease is remarkably different under two different circumstances and some factor(s) can be identified in one circumstance, but is absent in the other, either this factor or its absence may have caused the disease. For example, lung cancer is very common among smokers, while it is less common among the non-smokers, leading to the hypothesis that smoking may be a risk factor for lung cancer.
Group A + Smoking → High incidence of disease
Group B without smoking → Low incidence of disease
Thus, it is hypothesised that smoking is associated with lung cancer.
b. Method of agreement: if a factor is common to a number of different circumstances, each of which have the diseases, then this factor may have some sort of relationship with the disease. For example, if cases with hepatitis A give the history of having drinking water from the same sources, before onset of illness, a hypothesis associating drinking water and hepatitis could be proposed. Other example is HIV infection, which was found to be common among injecting drug users (IDUs), haemophiliacs and recipients of blood transfusion. This finding raised the possibility of spread of HIV infection through blood and blood products.
Situation 1: A + B + C + D → Disease present
Situation 2: A + X + Y + Z → Disease present
c. Method of concomitant variation: this method involves a factor, variation (frequency and intensity) of which causes variation in frequency of disease. Correlational studies provide useful data for the formulation of such hypothesis. For example,
Group A + high intensity of sun light → High incidence of skin cancer
Group B + low intensity of sun light → Low incidence of skin cancer
1. Descriptive studies: In descriptive studies, the pattern of disease occurrence is described in terms of time, place and person. Descriptive studies utilise information from diverse sources of data such as census, vital statistical records, hospital records as well as national figures about consumption of food, medications and other products. Descriptive studies are conducted especially to understand the disease pattern, extent of the problem and to generate research questions and hypothesis. Descriptive studies are generally less expensive and time-consuming than the analytic studies. Types of descriptive studies are
a. Case reports and case series
b. Correlational study
c. Cross-sectional study
2. Analytic studies: are conducted to identify the risk factor(s) for diseases or evaluate the interventions for control of disease(s) or other health problems. The analytic studies include:
a. Observational studies: such as, case-control and cohort studies
b. Experimental: such as, intervention trials (clinical trial and community trial)
1.1 Case report and case series:
Case reports and case series are the most frequently published articles in the medical journals. Case reports and case series usually describe the experience of a single patient (case report) or a group of patients (case series) with a similar disease. Case report documents unusual medical occurrences and can represent the first clues in the identification of new disease or adverse effects of medications (e.g., emergence of new disease like AIDS, thalidomide tragedy and use of oral contraceptive and development of venous thrombosis etc.). Case series are collections of individual case reports, which may occur, in fairly a short period of time. Such studies are important especially to identify the beginning or presence of an epidemic in the community. These types of studies where there are unusual features of disease (or patient’s history) may lead into generation of hypothesis. Although such studies provide important clues for generation of hypothesis, they cannot be tested because of lack of an appropriate comparison group. It is therefore necessary to design an appropriate analytic study to identify the possible factor.
1.2 Correlational study:
Also called ecological study. In this study design, the investigator collects or uses information from a community (or country) as whole rather than from individuals and search for associations among various factors present in the community. Main features of such study design are:
- It usually compares mortality or disease prevalence in different groups of people or community or country
- The unit of observation is the entire community (or country)
- The estimated exposure level found in that community or geographical unit is a surrogate measure for exposure of all individuals in that unit
- Linkage between individual exposure and individual suffering for a certain disease (or death) cannot be ascertained
Once information is collected, scatter diagram of morbidity (or mortality) rates against the average exposure rates in each community (or country or geographical areas) is constructed to assess possible association between exposure and outcome of interest. Other measures of association, such as correlation coefficient, coefficient of determination, are also calculated to quantify the relationship between the variables of interest and outcome. Such studies especially help to generate hypothesis between exposure and disease association. For example, to describe the pattern of morbidity of coronary heart disease (CHD) in 1960, death rates from 44 states (in US) were collected with per capita cigarette sales. It was observed that the death rates were highest in states with most cigarette sales, lowest in those with the least sales, and intermediate in the remainder. This observation contributed to the formulation of hypothesis that cigarette smoking causes fatal CHD, which has been documented subsequently in large number of analytic studies.
The advantages of such study is that it utilises the available data from different sources for analysis, thus can be conducted with minimum time and resources. However, the limitations of such studies are a) unable to link exposure with disease among individuals; b) correlational study presents average exposure of values rather than actual individual levels and c) subjected to potential confounding bias, which cannot be controlled during analysis. For example, a correlational study found association between increased pork consumption and breast cancer. Increased pork consumption may merely be a marker for a number of other factors for the increased risk of breast cancer, such as increased dietary fat, decreased vegetable intake or higher socio-economic status of people. It is not possible to separate the effects of such potential confounding factors while analysing data.
1.3 Cross-sectional study:
Also called prevalence survey. Main objective of such study is to describe the pattern of disease prevalence (not incidence) in the community at a certain point in time as well as to test association between possible risk factors with the disease for generation of hypothesis to be tested by analytical studies. Cross sectional study measures the exposure status and disease among the individuals at the same time. In many cases it is therefore not possible to determine whether the exposure preceded or resulted from the disease. For example, a cross sectional study found association between serum retinol (vitamin A) level and colonic cancer. It is very difficult to say from the cross sectional data whether low serum retinol is responsible for development of colonic cancer or it is the consequence, due to change in dietary habits. Such type of dilemma is common virtually in all the cross sectional studies.
Cross-sectional study reflects current status of health of a community. Such study is valuable both to the public health administrator (programme personnel) as well as to the epidemiologist. Cross sectional study findings are utilised by the health planers to understand the health status of the community, extent and distribution of health problems, priority setting, efficient allocation of resources and planning for intervention, while epidemiologist utilise the findings to identify the possible risk factors to design analytical studies to confirm them and provide recommendations on preventive interventions. For example, in Bangladesh Demographic and Health Survey is conducted every two years, collecting information through household interviews from a random sample of the population. It provides valuable information on population, fertility, mortality, nutritional status, child health and maternal health for effective health care planning and administration.
Cross sectional survey can also be utilised to determine the prevalence of disease or other health outcome in a specific group of people, such as in certain occupation. Such survey provides information on occupational exposure and frequency of disease.
1.3.1 Conduction:
Cross sectional survey is usually conducted by taking a sample from the defined population of interest. If the population size is small whole population may be studied provided there is enough resources available for this. To have a representative sample of the population, sample may be selected through either of the methods such as a) simple random sampling; b) systematic sampling; c) stratified random sampling and d) cluster sampling. Once the sample is selected, data are collected from the study subjects through a) questionnaire interview; b) observation; c) physical examination; and d) lab examinations.
1.3.2 Data analysis:
As mentioned earlier, from the cross sectional study we can only calculate the prevalence of disease in the community. Data are analysed mostly in terms of descriptive statistics and presented in the form of table, graphs or charts. We can also find association between the factor(s) of interest and the disease using appropriate statistical methods.
Example:
To determine the prevalence of sputum positive tuberculosis (TB) in a community, a random sample of 400 individuals (age more than 10 years) have been selected who gave history of cough for more than 2 weeks. Morning sputum from all of them was collected and was checked for AFB (acid-fast bacillus). Out of 400 sputum collected, AFB was found in the sputum of 32 individuals. Therefore, prevalence of sputum positive TB in the community is
Prevalence of sputum +ve TB = (32 400) X 100 or 8%
Data of the survey are cross classified by sex and is given in the following table.
AFB in sputum
+Ve -Ve Total
11
(a)
239
(b) 250
(a+b)
Male
21
(c)
129
(d) 150
(b+d)
Female
Total 32 368 400
Now we can compute prevalence rates among males and females as follows:
Prevalence rate among males
= [a (a + b)] X 100,
or, (11 250) X 100 or 4.4%;
Prevalence rate among females = [c (c + d)] X 100,
or (21 150) X 100 or 14.0%
Data clearly indicate that the prevalence of TB is much higher among the females compared to the males. As these (prevalence rates) are not the direct measures of the disease frequency (incidence rates) among males and females, we cannot really compute the relative risk. However, we can find association between TB and sex by using the Chi-square test, formula for which is as follows:
2 = [n (ad – bc)2] [(a + b) (c + d) (a + c) (b + d)]
In our example, 2 = 11.7, which is much higher than the tabulated value (3.841 with df 1). Therefore, we can say that there is association between sex and sputum positive TB in the community.
In the same manner, association between other factor(s) of interest and TB can be determined.
1.3.3 Advantages and disadvantages of cross-sectional studies:
Advantages:
- Can be conducted quickly and easily with limited resources.
- Provides possible means to find association between possible risk factors and disease without question of temporality, particularly for the permanent characteristics of the individuals (e.g., sex, race, blood group etc.).
Disadvantages:
- Only provides information about disease prevalence but not the incidence of disease in the community
- It provides “snapshot” information about the community at a specific point in time
- In most instances, causal relationship between a factor and disease cannot be determined
- It requires well planned sampling scheme to generalise the findings
- There are also problem of non-response for such kind of study design
3. Hypothesis formulation from descriptive studies:
For any public health problem, first step in the search for possible solutions is to formulate a reasonable and testable hypothesis. There are three methods of hypothesis formulation about disease aetiology as described below.
a. Method of difference: involves reasoning that disease frequency is different in two sets of circumstances. If frequency of a disease is remarkably different under two different circumstances and some factor(s) can be identified in one circumstance, but is absent in the other, either this factor or its absence may have caused the disease. For example, lung cancer is very common among smokers, while it is less common among the non-smokers, leading to the hypothesis that smoking may be a risk factor for lung cancer.
Group A + Smoking → High incidence of disease
Group B without smoking → Low incidence of disease
Thus, it is hypothesised that smoking is associated with lung cancer.
b. Method of agreement: if a factor is common to a number of different circumstances, each of which have the diseases, then this factor may have some sort of relationship with the disease. For example, if cases with hepatitis A give the history of having drinking water from the same sources, before onset of illness, a hypothesis associating drinking water and hepatitis could be proposed. Other example is HIV infection, which was found to be common among injecting drug users (IDUs), haemophiliacs and recipients of blood transfusion. This finding raised the possibility of spread of HIV infection through blood and blood products.
Situation 1: A + B + C + D → Disease present
Situation 2: A + X + Y + Z → Disease present
c. Method of concomitant variation: this method involves a factor, variation (frequency and intensity) of which causes variation in frequency of disease. Correlational studies provide useful data for the formulation of such hypothesis. For example,
Group A + high intensity of sun light → High incidence of skin cancer
Group B + low intensity of sun light → Low incidence of skin cancer
BASIC EPIDEMIOLGY
EPIDEMILOGY & PUBLIC HEALTH
Organized community efforts aimed at the prevention, preservation, Rehabilitation and promotion of health.
It links many disciplines and depends upon the scientific TOOLS of “EPIDEMIOLOGY”.
PUBLIC HEALTH SURVEILLANCE:
Systematically collects, analyses, interprets and disseminates health data:
DISEASE INVESTIGATION
ANALYTIC STUDIES
EVALUATION -
Effectiveness
Efficiency
OBJECTIVES
1. Define hygiene and describe epidemiological measure to assess burden of
disease in the community.
2. Describe epidemiology of tropical diseases and approach to prevention and control.
3. Describe nutritional problems in the tropics and discussed detection of these problems as well as its management.
4. Describe common environmental and occupational health and measures of prevention.
What is Epidemiology?
Simply : It is the study of health and disease in human populations.
Comprehensively : It is the study of the distribution and determinants of disease frequency in human populations.
WHAT is the event? (the problem)
WHAT is the magnitude?
WHERE did it happen?
WHO are affected?
WHY did it happen?
FIVE main objectives of Epidemiology
1. To identify the cause of disease and its risk factors
2. To determine the extent of disease found in the community
3. To study the natural history and prognosis of disease
4. To evaluate new preventative and therapeutic measures
5. To provide a foundation for developing public policy.
SCOPE OF EPIDEMIOLOGY
Epidemiologic study can be applied to all diseases, conditions and health related events. ex. - Infectious diseases - Study of epidemics - Cardiovascular diseases
- Malignant Diseases - Accidents and injuries -Nutritional disorders
--Emerging & Re-emerging Disease
• Mental illnesses, • Congenital defects, • Drug addictions, • Family planning
• Vaccine Development, • Health services research, • Disease Surveillance
• Disease Forecasting
AIMS
According to the International Epidemiological Association (IEA), epidemiology has three main aims:
1. To describe the distribution and magnitude of health and disease problems in
human populations
2. To identify etiological factors (risk factors) in the pathogenesis of disease
3. To provide the data essential to the planning, implementation and evaluation of
services for the prevention, and control and treatment of disease and to the
setting up of priorities among those services.
PURPOSE OF EPIDEMIOLOGY
1.Provision of data necessary for planning and evaluating health care
2.Identification of determinants of disease so as to enable prevention
3.Evaluation of methods used to control disease
4.Description of natural history of disease
5.Classification of disease
FUNCTIONS OF EPIDEMIOLOGY
1. To discover the agent, host and environmental factors which affect health, in order to provide the scientific basic for the prevention of disease and injury and promotion of health
2. To determine the relative importance of causes of illness, disability and death, in order to establish priorities for research and action
3. To identify those sections of the population which have greatest risk from specific causes of ill health, in order that the indicated action may be directed appropriately
4. To evaluate the effectiveness of health programs and services in improving the health of the population
TROPIC
The name of 2 circles of celestial sphere; each 23.5o distant from the EQUATOR.
Tropic of cancer (the northern)
Tropic of capricorn (the southern)
Regions lying between the tropic of cancer and tropic of Capricorn
TROPICAL ZONE: The regions lying between the tropic of cancer and the tropic of Capricorn
TROPIC
Two circles of the celestial sphere, each 23.5o distant from the equator, the northern one is called the tropic of cancer, and the southern the tropic or Capricorn.
Tropical Medicine
The branch of medicine that deals with diseases, mainly of parasitic origin, of tropical countries.
DEFINITION OF HYGIENE
DEFINITION : the Science and Art of Preserving and Improving Health
• The aim is to impart knowledge and teach the means of improving one’s
health
• Deals with individuals as well as the community as a whole
Public Health
The art and science of maintaining protecting and improving the health of the people through organized community efforts.
SANITATION is the branch of public health which is concerned with keeping the external environment healthful
Distribution
•Age, sex, race, occupational and social characteristics, place of residence, ect. The pertinent characterisitcs
•the time, place, person distribution
Determinants
• The necessary causes and enabling factors
• Agent factor - necessary factors
• host factors : age, sex, race, genetic makeup, pregnancy, previous immunologic experience
Environmental factors : family size and composition, crowding, hygienic conditions, geographic, climatic and seasonal circumstances, “lifestyle” -qualities of society
HOW ???
ASKING QUESTIONS MAKING COMPARISONS
Who? Exposure and Risk (Disease)
What?
When?
Where? Before and After (Intervention)
Why?
How?
DESCRIPTIVE STUDIES
First phase of epidemiological investigation
Concerned with observing the distribution of disease or health-related characteristics
Identifying characteristics with the disease seems to be associated with objective to formulate hypothesis
Procedures in Descriptive Studies:
Defining the population to be studies, Defining the disease under study, Describing the disease by time, place, person; Measurement of disease Comparing with known indices, Formulation of etiologically hypothesis
ANALYTICAL EPIDEMIOLOGY
• Second major type of epidemiological studies
• The subject of interest is the individual within the population
• The objective is to test hypotheses
• The inference made is to the population from which the sample was drawn
Organized community efforts aimed at the prevention, preservation, Rehabilitation and promotion of health.
It links many disciplines and depends upon the scientific TOOLS of “EPIDEMIOLOGY”.
PUBLIC HEALTH SURVEILLANCE:
Systematically collects, analyses, interprets and disseminates health data:
DISEASE INVESTIGATION
ANALYTIC STUDIES
EVALUATION -
Effectiveness
Efficiency
OBJECTIVES
1. Define hygiene and describe epidemiological measure to assess burden of
disease in the community.
2. Describe epidemiology of tropical diseases and approach to prevention and control.
3. Describe nutritional problems in the tropics and discussed detection of these problems as well as its management.
4. Describe common environmental and occupational health and measures of prevention.
What is Epidemiology?
Simply : It is the study of health and disease in human populations.
Comprehensively : It is the study of the distribution and determinants of disease frequency in human populations.
WHAT is the event? (the problem)
WHAT is the magnitude?
WHERE did it happen?
WHO are affected?
WHY did it happen?
FIVE main objectives of Epidemiology
1. To identify the cause of disease and its risk factors
2. To determine the extent of disease found in the community
3. To study the natural history and prognosis of disease
4. To evaluate new preventative and therapeutic measures
5. To provide a foundation for developing public policy.
SCOPE OF EPIDEMIOLOGY
Epidemiologic study can be applied to all diseases, conditions and health related events. ex. - Infectious diseases - Study of epidemics - Cardiovascular diseases
- Malignant Diseases - Accidents and injuries -Nutritional disorders
--Emerging & Re-emerging Disease
• Mental illnesses, • Congenital defects, • Drug addictions, • Family planning
• Vaccine Development, • Health services research, • Disease Surveillance
• Disease Forecasting
AIMS
According to the International Epidemiological Association (IEA), epidemiology has three main aims:
1. To describe the distribution and magnitude of health and disease problems in
human populations
2. To identify etiological factors (risk factors) in the pathogenesis of disease
3. To provide the data essential to the planning, implementation and evaluation of
services for the prevention, and control and treatment of disease and to the
setting up of priorities among those services.
PURPOSE OF EPIDEMIOLOGY
1.Provision of data necessary for planning and evaluating health care
2.Identification of determinants of disease so as to enable prevention
3.Evaluation of methods used to control disease
4.Description of natural history of disease
5.Classification of disease
FUNCTIONS OF EPIDEMIOLOGY
1. To discover the agent, host and environmental factors which affect health, in order to provide the scientific basic for the prevention of disease and injury and promotion of health
2. To determine the relative importance of causes of illness, disability and death, in order to establish priorities for research and action
3. To identify those sections of the population which have greatest risk from specific causes of ill health, in order that the indicated action may be directed appropriately
4. To evaluate the effectiveness of health programs and services in improving the health of the population
TROPIC
The name of 2 circles of celestial sphere; each 23.5o distant from the EQUATOR.
Tropic of cancer (the northern)
Tropic of capricorn (the southern)
Regions lying between the tropic of cancer and tropic of Capricorn
TROPICAL ZONE: The regions lying between the tropic of cancer and the tropic of Capricorn
TROPIC
Two circles of the celestial sphere, each 23.5o distant from the equator, the northern one is called the tropic of cancer, and the southern the tropic or Capricorn.
Tropical Medicine
The branch of medicine that deals with diseases, mainly of parasitic origin, of tropical countries.
DEFINITION OF HYGIENE
DEFINITION : the Science and Art of Preserving and Improving Health
• The aim is to impart knowledge and teach the means of improving one’s
health
• Deals with individuals as well as the community as a whole
Public Health
The art and science of maintaining protecting and improving the health of the people through organized community efforts.
SANITATION is the branch of public health which is concerned with keeping the external environment healthful
Distribution
•Age, sex, race, occupational and social characteristics, place of residence, ect. The pertinent characterisitcs
•the time, place, person distribution
Determinants
• The necessary causes and enabling factors
• Agent factor - necessary factors
• host factors : age, sex, race, genetic makeup, pregnancy, previous immunologic experience
Environmental factors : family size and composition, crowding, hygienic conditions, geographic, climatic and seasonal circumstances, “lifestyle” -qualities of society
HOW ???
ASKING QUESTIONS MAKING COMPARISONS
Who? Exposure and Risk (Disease)
What?
When?
Where? Before and After (Intervention)
Why?
How?
DESCRIPTIVE STUDIES
First phase of epidemiological investigation
Concerned with observing the distribution of disease or health-related characteristics
Identifying characteristics with the disease seems to be associated with objective to formulate hypothesis
Procedures in Descriptive Studies:
Defining the population to be studies, Defining the disease under study, Describing the disease by time, place, person; Measurement of disease Comparing with known indices, Formulation of etiologically hypothesis
ANALYTICAL EPIDEMIOLOGY
• Second major type of epidemiological studies
• The subject of interest is the individual within the population
• The objective is to test hypotheses
• The inference made is to the population from which the sample was drawn
Subscribe to:
Posts (Atom)