Epidemiology of Cholera

Dr Hafsa Raheel MBBS,MCPS,FCPSDepartment 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 (1813-1858)

Regarded as the fatherof epidemiology (i.e.study of the spread ofdisease)

Has a London pubnamed after him (TheJohn Snow)

Cholera in London

• In 1854, the Queen’sphysician, John Snow,investigated anoutbreak of cholera inthe Broad Street Area.

• He charted thefatalities and focusedon a communaloperated hand waterpump

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 undoubtedlycontamination of thewater supply with sewage

• This is a problemwhich haunts societyeven in 2006

Acute intestinal infection caused by the bacterium Vibrio cholera characterized by:

Copious painless diarrhea and vomiting

Cholera

http://gamapserver.who.int/mapLibrary/app/searchResults.aspx

Current epidemic7th 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 - 25-50%

• Case fatality with treatment (ORS) - 1%

Spectrum of disease

• Incubation period: 1-5 days

• Modes of transmission:1-Contaminated water and food2-Rarely direct from person to person

• Reservior1-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 efficacyo not recommended for use in endemic areas, during outbreaks, or in

people traveling to endemic areas.

oOral 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 pain

• Disease progresses:– High grade fever (greater than 103 degrees Fahrenheit)– Diarrhea becomes prominent– Weakness– profound fatigue – Delirium, and an acutely ill appearance develop. – 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 chest

Exams and Tests   

• An elevated white blood cell count in blood • A blood culture during first week of the fever can show S.

typhi bacteria • A stool culture • An ELISA test on urine may show Vi antigen specific for

the bacteria • A platelet count (decreased platelets ) • A fluorescent antibody study (demonstrates Vi antigen,

which is specific for typhoid)

Treatment 

• Intravenous fluids and electrolytes may be given

• 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) • Intestinal perforation • Kidney failure

• Peritonitis

Incubation period:

• 10-14 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