Confirmed and suspected cases shall be reported immediately to the local Health Unit.
Cholera is caused by toxigenic strains of Vibrio cholerae, which is a gram-negative, curved rod that is motile and has many serogroups. Only the toxin producing serogroups O1, O139 cause epidemics. However, non-toxigenic serotypes such as O141 can cause sporadic illness.
Most persons infected with cholera do not become ill, although the bacterium is present in their feces for 7–14 days. When illness does occur, infection causes only mild or moderate diarrhea in roughly 90% of individuals. In 5–10% of cases, infected individuals develop severe, watery diarrhea and vomiting. Stools are typically colourless with flecks of mucous referred to as “rice water” diarrhoea. The resulting loss of fluids in an infected individual can rapidly lead to severe dehydration. If not treated, death can occur within hours.
Modes of Transmission
Cholera is one of the oldest and best understood epidemic diseases. Epidemics and pandemics are strongly linked to the consumption of fecally contaminated water.
Transmission occurs through the ingestion of food or water contaminated with feces or vomitus of cases or carriers; consumption of raw or improperly cooked seafood, and other foods harvested from estuarine water or seawater.
From a few hours to 5 days, usually 2–3 days.
Period of Communicability
For the duration of the stool-positive stage, usually until 2–3 days after recovery for symptomatic individuals, however, carrier state may persist for months. Asymptomatic individuals can shed the bacterium in their feces for 7–14 days. Appropriate antibiotics can shorten the period of communicability, but are not recommended for treatment.
Susceptibility is variable; gastric achlorydia and the lack of immunity seen in small children may increase the risk of illness. Breastfed infants are at a reduced risk of cholera. Cholera occurs more often in persons with blood type O.
In endemic areas, most people acquire antibodies by early adulthood. Infection with O1 serogroup affords no protection against O139 infection and vice versa. Previous exposure does not confer immunity against future infection.
Diagnosis and Laboratory Testing
Diagnosis is confirmed by laboratory isolation of cholera toxin producing Vibrio cholera serovar O1 or O139 from an appropriate specimen (e.g. stool) OR by detection of V. cholerae by nucleic acid amplification testing (NAAT) from an appropriate clinical specimen (stool).
Treatment and Case Management
Treatment is under the direction of the attending health care provider.
Exclude infected persons from high risk settings (food preparation, daycare and health care) until 24 hours after cessation of symptoms, and 48 hours after antibiotic therapy or anti-diarrheal medications.
Meal companions in the 5 days before onset should be assessed for symptoms and advised to seek medical care if indicated. Chemoprophylaxis of contacts currently is not recommended by the WHO, except in special circumstances in which the probability of fecal exposure is high and medication can be delivered rapidly.
Management of symptomatic contacts is the same as for cases.
Heymann, D.L. Control of Communicable Disease Manual (19th Ed.). Washington, American Public Health Association, 2008.