Cholera

Vibrio cholerae is a Gram-negative organism that can be subdivided into over 200 serogroups based on the somatic O antigen, with only serogroups O1 and O139 causing epidemic and pandemic disease. Historically it has killed millions from dehydrating diarrhoea, encouraged the birth of modern epidemiology, the sanitary revolution, and oral rehydration therapy; it persists today as a glaring reminder of poverty and inadequate water/sanitation. Contaminated food (especially undercooked seafood) is the usual route of transmission in developed countries; contaminated water and street food vendors are more common vehicles in less developed countries.

Clinical features and diagnosis—typical presentation is with sudden onset of voluminous, painless, watery diarrhoea, which can exceed 500 to 1000 ml/h, leading to severe dehydration in a couple hours and risk of death. Definitive diagnosis is by isolating V. cholerae from stool or rectal swab samples.

Treatment—oral rehydration therapy with sugar or starch, water, and salts must be provided in the community and at field stations, clinics, and hospitals where most patients present: this reduces the case fatality of untreated severe cholera from about 50% to 1% or less. Antibiotics can shorten the illness and decrease diarrhoeal purging: tetracycline, cotrimoxazole, ciprofloxacin, or azithromycin have been effective, but there is increasing resistance.

Prevention—effective preventive measures include (1) ensuring a safe water supply; (2) improving sanitation; (3) making food safe for consumption by thorough cooking of high-risk foods, especially seafood; and (4) health education through mass media. Newer-generation killed oral cholera vaccines have been licensed and proved to be well tolerated, protective, cost-beneficial, and a potential tool to control cholera together with the other preventive recommendations.