Cholera

28 August 2012

Key facts

  • Cholera is an acute diarrhoeal disease that can kill within hours if left untreated.
  • There are an estimated 3–5 million cholera cases and 100,000-120,000 deaths due to cholera every year.
  • Up to 80% of cases can be successfully treated with oral rehydration salts.
  • Effective control measures rely on prevention, preparedness and response.
  • Provision of safe water and sanitation is critical in reducing the impact of cholera and other waterborne diseases.
  • Oral cholera vaccines are considered an additional means to control cholera, but should not replace conventional control measures.

What is cholera?

Cholera is an acute bacterial enteric disease caused by ingestion of food or water contaminated with the bacteria Vibrio cholerae. It has a short incubation period from a few hours to 5 days.

Cholera is an extremely virulent disease. It affects both children and adults and can kill within hours. People with low immunity – such as malnourished children or people living with HIV – are at a greater risk of death if infected.

What are the symptoms of cholera?

Severe cases are characterized by:

  • sudden onset of acute painless watery diarrhoea
  • nausea and profuse vomiting early in the course of illness

Dehydration and shock can occur because of a rapid loss of body fluid, and without treatment death may occur. The extremely short incubation period - two hours to five days - enhances the potentially explosive pattern of outbreaks, as the number of cases can rise very quickly.

About 75% of people infected with V. cholerae do not develop any symptoms, although the bacteria are present in their faeces for 7–14 days after infection and are shed back into the environment, potentially infecting other people. Among people who develop symptoms, 80% have mild or moderate symptoms, while around 20% develop acute watery diarrhoea with severe dehydration. This can lead to death if untreated.

How do people get cholera?

  • Cholera is usually transmitted through faecally-contaminated water or food, dirty hands, vomit or stools of sick people.
  • New outbreaks can occur sporadically in any part of the world where water supply, sanitation, food safety, and hygiene are inadequate.
  • The greatest risk occurs in over-populated communities and refugee settings or evacuation centres characterized by poor sanitation, unsafe drinking-water, and increased person-to-person transmission.
  • Because the incubation period is very short (2 hours to 5 days), the number of cases can rise extremely quickly.

What is the treatment for cholera

Treatment is straightforward (basically rehydration) and, if applied appropriately, should keep case-fatality rate below 1%.

  • Oral rehydration salts (ORS) should be promptly administered to cholera patients. Cholera is an easily treatable disease where up to 80% of people can be treated successfully with ORS.
  • Very severely dehydrated patients require administration of intravenous fluids. Such patients also require appropriate antibiotics to diminish the duration of diarrhoea, reduce the volume of rehydration fluids needed, and shorten the duration of V. cholerae excretion.
  • For children up to five years, supplementary administration of zinc has a proven effective in reducing duration of diarrhoea as well as reduction in successive diarrhoea episodes.
  • Mass administration of antibiotics is not recommended, as it has no effect on the spread of cholera and contributes to increasing antimicrobial resistance.

In order to ensure timely access to treatment, cholera treatment centres (CTCs) should be set up among the affected populations.

How can cholera be prevented?

Measures to prevent transmission of cholera include the following:

  • Provision of safe water, proper sanitation (including the necessity of systematic hand-washing with soap after defecation and before handling food or eating) and food safety are critical for preventing occurrence of cholera.
  • Health education aims at communities adopting preventive behaviour for averting contamination.

Is oral cholera vaccination recommended?

There are two types of safe and effective oral cholera vaccines currently available on the market. Both are whole-cell killed vaccines, one with a recombinant B-sub unit, the other without. Both have sustained protection of over 50% lasting for two years in endemic settings. Both vaccines are WHO-prequalified and licensed in over 60 countries.

  • Dukoral has been shown to provide short-term protection of 85–90% against V. cholerae O1 among all age groups at 4–6 months following immunization.
  • The other vaccine (Shanchol) provides longer-term protection against V. cholerae O1 and O139 in children under five years of age.
  • Both vaccines are administered in two doses given between seven days and six weeks apart. The vaccine with the B-subunit (Dukoral) is given in 150 ml of safe water.

Immunization with currently available cholera vaccines should be used in conjunction with the usually recommended control measures in areas where cholera is endemic as well as in areas at risk of outbreaks. Vaccines provide a short term effect while longer term activities like improving water and sanitation are put in place. When used, vaccination should target vulnerable populations living in high risk areas and should not disrupt the provision of other interventions to control or prevent cholera epidemics.

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