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Cholera

Epidemiology of Infectious Diseases: Cholera

Causal Agent
Vibrio cholerae bacteria, serogroups 01 and 0139

Common Clinical Features

  • Symptoms range from mild to moderate diarrhoea (80-90% of cases) to the severe sudden onset of profuse watery diarrhoea (rice water stool) accompanied by nausea and vomiting.
  • In severe cases rapid dehydration, leading to circulatory shock and possible death. In such cases immediate fluid and electrolyte replacement is required.
  • Severe untreated cases have a 50% mortality, but <1% fatality with the correct treatment.

Geographical Distribution

  • Prevalent in developing countries where sanitation and food and water hygiene are inadequate or lacking, particularly in areas effected by natural disaster, war and migration of refugees.
  • Worldwide there have been 7 major pandemics in the last 200 years. The current seventh pandemic (due to V. cholerae 01, biotype El Tor) began in 1961. Since which time it has spread through Asia, Africa and Latin America.
  • Since 1992 V. cholerae 0139, a previously unidentified serogroup has been identified as the cause of outbreaks in India and Bangladesh and reported in 11 countries of South East Asia1.
  • In 2002 WHO reported 142,311 cases and 4564 deaths from cholera worldwide.
  • Cholera is rare in industrialised countries. Between 1990 and 2000 only 80 cases of imported cholera were notified in the UK2. The risk to international travellers is low.

Reservoir
The main reservoir is humans.

Mode of Transmission

  • Faecal-oral route.
  • The ingestion of food or water contaminated by faeces or vomitus of an infected person.
  • Raw or undercooked contaminated seafood.

Incubation Period
<1 to 5 days, commonly 2-3 days.

Period of Communicability

  • Individuals remain infectious during period of diarrhoea and for up to 7 days after.
  • The carrier state may persist in a few cases for up to a few months.  

Prevention and Control
Advice to overseas travellers on food and water hygiene.

References

  1. World Health Organization. Cholera, Fact sheet N0107, March 2000.
     
  2. Hawker J, Begg N, Blair I, Reintjes R, Weinberg J. Communicable Disease Control Handbook, Blackwell, 2005.

© CM Kirwan 2006