Epidemiology of Cholera Dr Hafsa Raheel MBBS,MCPS,FCPS Department of Family and Community Medicine King Saud University

Case scenerio In 1989/90, 243 infected (4 died) in BurdineTownship, Missouri Possibly cause: contamination of municipal water supply Cases declined after residents boiled their water, and after chlorination of water supply.

John Snow ( ) Regarded as the father of epidemiology (i.e. study of the spread of disease) Has a London pub named after him (The John Snow)

Cholera in London In 1854, the Queen’s physician, John Snow, investigated an outbreak of cholera in the Broad Street Area. He charted the fatalities and focused on a communal operated hand water pump

Cholera (1854) Snow convinced the Board of Guardians to remove the handle The result was a sudden and dramatic incidence of cholera Hundreds were infected and died Incidentally, beer drinkers remained healthy!

Cholera (1854) There was undoubtedly contamination of the water supply with sewage This is a problem which haunts society even in 2006

Acute intestinal infection caused by the bacterium Vibrio cholera characterized by: Copious painless diarrhea and vomiting Cholera

Current epidemic 7 th epidemic Due to V cholerae 01, V eltor & V cholerae 0139 Started 1961 in Indonesia. Bangladesh 1963 India 1964 West Africa 1970 Latin America 1991 Bangladesh 1992 (V cholerae 0139) South East Asia South Africa 2000

Infectious agent: Vibrio cholerae Serogroup O1: epidemic cholera is caused by two biotypes of Vibrio cholerae serogroup O1: –the classical biotype, and –since 1961 (7th pandemic), the biotype El Tor Serogroup O1 includes serotypes Inaba, Ogawa and Hikojima Serogroup O139: in 1992/93, a new Vibrio cholerae O139 strain appeared

Sub clinical (excrete the organism in faeces for 7-14 days) 10% of the infected - typical cholera 90% of episodes - mild or moderate Case fatality without treatment % Case fatality with treatment (ORS) - 1% Spectrum of disease

Incubation period: 1-5 days Modes of transmission: 1-Contaminated water and food 2-Rarely direct from person to person Reservior 1-Aquatic environment (Brackish water & sea food) 2-Human beings Communicability (stool-positive stage): Usually ends few days after recovery, occasionally several months carrier state, antibiotics can shorten the period of communicability Epidemiology of Disease

Prevention and control Hygienic disposal of human faeces Adequate supply of safe drinking water Good food hygiene -Cooking food thoroughly & eating it hot -Prevent contact of cooked food with raw contaminated food, water or ice -Avoid raw vegetables unless peeled Boil it, cook it, peel it or forget it - Mass chemoprophylaxis has no effect

o The previous parenteral cholera vaccines: o little efficacy o not recommended for use in endemic areas, during outbreaks, or in people traveling to endemic areas. o Oral immunization: (1) killed bacterial vaccines (2) live genetically engineered mutants deleted of toxin genes (3) avirulent vectors genetically engineered to express protective cholera antigens. Vaccination

Epidemiology of Typhoid fever

Salmonella typically produces 3 distinct syndromes: food poisoning, typhoid fever & asymptomatic carrier state. Salmonella gastroenteritis manifest as vomiting & diarrhea within 6-48 hours after ingestion of food or drink contaminated with bacteria. SALMONELLOSIS It is self-limiting, treatment is by water & salts replacement. Antibiotics are not usually needed.

Typhoid fever Causal agent: Salmonella enterica subsp.enterica serovar typhi An obligate human pathogen May occur in the digestive tract without showing any signs of disease Transmitted via human excreta (food handlers!!) Common in the developing world

Sign and symptoms Early symptoms –fever, malaise and abdominal painfevermalaiseabdominal pain Disease progresses: –High grade fever (greater than 103 degrees Fahrenheit) –Diarrhea becomes prominentiarrhea – WeaknessWeakness –profound fatiguefatigue –Delirium, and an acutely ill appearance develop.elirium –A rash, characteristic only of typhoid and called "rose spots," appears in some cases of typhoid. Rose spots are small (1/4 inch) red spots that appear most often on the abdomen and chestrash

Exams and Tests An elevated white blood cell count in blood A blood culture during first week of the fever can show S. typhi bacteriablood culture A stool culturestool culture An ELISA test on urine may show Vi antigen specific for the bacteriaELISAantigen A platelet count (decreased platelets )platelet countplatelets A fluorescent antibody study (demonstrates Vi antigen, which is specific for typhoid)antibody

Treatment Intravenous fluids and electrolytes may be givenIntravenouselectrolytes Appropriate antibiotics are given to kill the bacteria CAUTION: There are increasing rates of antibiotic resistance throughout the world, so the choice of antibiotics should be a careful one

Possible Complications Intestinal hemorrhage (severe GI bleeding)GI bleeding Intestinal perforation Kidney failure Peritonitis

Incubation period: days. Peak age 4-19 years Modes of transmission: Water contaminated with fecal materials. Contaminated food. Food handlers. Reservoir: Only human (cases & carriers) Epidemiology of typhoid fever

NURSING CARE Isolation & barrier nursing is indicated Trace source of infection. continue breastfeeding infants & young children and give ORS & light diet for other patients in the first 48 hours. Notification of the case to the infection control nurse in the hospital.

PREVENTION Education on hygiene practices like hand washing after toilet use & avoidance of eating in non hygienic restaurants. Antibiotic prophylaxis is not needed for house-hold contacts. Proper handling & refrigeration of food even after cooking. Salmonella TAB vaccine is available but affectivity is low (50% claimed protection).

Indication of vaccination: –Travellers to endemic areas – People in refugee camps – Microbiologists. Treatment: Antibiotics : Ciprofloxacin, pefloxacin & cephalosporins