Cause
Vibrio cholerae bacteria, serogroups O1 and O139.
Transmission
Infection occurs through ingestion of food or water contaminated directly or indirectly by faeces or vomitus of infected persons. Cholera affects only humans; there is no insect vector or animal reservoir host. Nature of the disease An acute enteric disease varying in severity. Most infections are asymptomatic (i.e. do not cause any illness). In mild cases, diarrhoea occurs without other symptoms. In severe cases, there is sudden onset of profuse watery diarrhoea with nausea and vomiting and rapid development of dehydration. In severe untreated cases, death may occur within a few hours due to dehydration leading to circulatory collapse.
Geographical distribution
Cholera occurs mainly in poor countries with inadequate sanitation and lack of clean drinking-water and in war-torn countries where the infrastructure may have broken down. Many developing countries are affected, particularly those in Africa and Asia, and to a lesser extent, those in central and South America.
Risk for travellers
Travellers are not at signifi cant risk from cholera provided that simple precautions are taken to avoid potentially contaminated food and water. Vaccination is of questionable benefi t to general tourist travellers, for whom the risk is very low, and is therefore recommended only for individuals at increased risk of exposure, particularly emergency relief and health workers in refugee situations. Cholera vaccination is not required as a condition of entry to any country.
Prophylaxis
Cholera vaccines for use by travellers and those in occupational risk groups are available in some countries.
Precautions
As for other diarrhoeal diseases. All precautions should be taken to avoid consumption of potentially contaminated food, drink and drinking-water. Oral rehydration salts should be carried to combat dehydration in case of severe diarrhoea.
Vaccine
Although two new cholera vaccines (live and killed), given orally, are safe and effective and have been licensed in a limited number of countries, the live vaccine is currently no longer available commercially. The killed, oral vaccine is safe and effi cacious for individuals over 2 years of age and confers high-grade (85–90%) protection for 6 months after the second dose, to be given at least 1 week after the fi rst. Protection declines rapidly in young children after 6 months, but remains as high as 62% in adult vaccine recipients.
Type of vaccine: Killed oral
Number of doses: Two, at least 1 week apart
Contraindications: Hypersensitivity to previous dose
Adverse reactions: Mild gastrointestinal disturbances reported
Before departure: 3 weeks
Consider for: Travellers at high risk (e.g. emergency or relief workers)
Special precautions: None