Cholera is an acute intestinal infection caused by the bacterium Vibrio cholerae. Epidemics of cholera have occurred over the centuries but have been largely eliminated from countries with safe water supplies & proper sanitation. Nevertheless we are currently in the midst of a pandemic which began in Indonesia in the sixties & in three decades has spread to Asia, the Middle East & Russia, Africa & South America. This pandemic is associated with the El Tor strain of the cholera vibrio but a number of other strains or sub-varieties can cause local outbreaks.
HOW THE DISEASE IS TRANSMITTED
Cholera is spread by water & food contaminated with the germ by unhygienic handling or by flies. . Sudden large outbreaks are usually caused by a contaminated water supply. The germ can survive in fresh water for days or even a few weeks. Unless conditions are particularly unhygienic direct person-to-person transmission is rare. Breastfeeding infants rarely get infected although it is mainly a disease of young children in affected populations. Carriers who have no symptoms play an important role in carrying V. cholerae from place to place, causing epidemics to spread. Marine shellfish & plankton concentrate the germ in areas where untreated sewage is discharged into the sea & become the main reservoirs of V.cholerae.
Most infected people do not become ill although the bacterium can be detected in the faeces for 1 - 2 weeks. When illness does occur more than 90% of cases have mild to moderate diarrhoea indistinguishable from other causes such as simple traveller's diarrhoea. Less than 10% develop the dramatic & frightening disease with copious, painless diarrhoea quickly leading to severe dehydration & death within hours or days, if treatment is not promptly given.
Oral rehydration solution (eg Gastrolyte, Replyte) properly made up in safe water is the first treatment of choice in cholera as in other forms of diarrhoea. Even during an epidemic 80 --90% of patients can be treated with rehydration by mouth. but in severe cases it will be necessary to have fluids given through the veins. Antibiotics such as doxycycline can reduce the volume & duration of diarrhoea, but death is due to dehydration & fluids are the first-aid treatment, the emergency treatment & the continued treatment.
Boiling water will kill the cholera organism as will filtered water treated with iodine or chlorine. Sealed bottled water with an identifiable label is safe. Do not trust any ice. Food that is thoroughly cooked & comes to you piping hot is safe. It is best to avoid shellfish. Avoid raw fruits & vegetables unless you can peel them or you are certain that they have been adequately washed. Avoid food that is likely to have been standing around & contaminated by flies. These are simple & time-tested precautions that will prevent cholera.
An effective 2 dose oral vaccine is now available, & this can provide good protection, 80%, for 2-3 years. Individuals at high-risk of disease should use this vaccine. Most routine travellers are not at significant risk of disease & do not need this vaccine. Use of this vaccine may give a false sense of security to vaccinated subjects who may then neglect more effective measures.
In 1973 the World Health Assembly deleted from the International Health Regulations the requirement for presentation of a cholera vaccination certificate. Today, no country requires proof of cholera vaccination as a condition for entry.