What is cholera?
Cholera is an acute diarrhoeal illness caused by a bacterium Vibrio cholerae. It is characterised by painless diarrhoea and vomiting. Most people infected with V. cholerae do not become ill. When illness occurs, 90% develop uncomplicated vomiting and diarrhoea. Fewer than 10% of cases develop the severe form of the disease, which, if not treated can be rapidly life threatening due to dehydration and shock. In severe cases, the diarrhoea can be very watery and profuse and it is this loss of fluid that can make the disease so serious.

How do you get cholera?
Cholera is usually contracted by drinking contaminated water or by eating contaminated food. Sudden large outbreaks are usually caused by a contaminated water supply. Its principal method of spread is through water. Outbreaks of cholera are most likely to occur where poor or non-existent sewage systems allow drinking water to become polluted with human waste. It may also be transmitted by food, particularly shellfish. This method is the commonest in the US, where cases arise in the Gulf Coast States periodically due to contamination of shellfish beds. Person to person spread is relatively uncommon, especially in developed countries. The greatest protection against cholera is safe potable chlorinated drinking water, uncontaminated by sewage. 

How serious is cholera?
Most people infected with cholera do not develop illness. Cholera, however, is a potentially fatal disease in those countries where it is endemic. It is less of a problem in those countries into which it is imported. Once the dehydration is rapidly treated, full recovery is usual. Even in less developed countries, when illness does occur, more than 90% of episodes are of mild or moderate severity and are difficult to distinguish clinically from other types of acute diarrhoea.

In developed countries with sophisticated healthcare systems, rapid treatment of dehydration and shock means that the fatality from cholera is quite uncommon. In fact, the fatality rate for cholera in developed countries such as the US is less than that for disease due to E.coli O157 or salmonellosis. Cholera is a notifiable disease in Ireland.

How common is cholera?
In 2001, more than 180,000 cases were reported to WHO. Cholera, however, is a very uncommon disease in Europe. In Western Europe, cases are invariably imported from endemic areas (areas where the disease is found naturally). Cholera is very uncommon in Ireland, with only single cases being seen in any year. Cases seen in Ireland are imported.

Is there more cholera around than in the past?
Cholera used to be very common in Ireland, Britain, Europe and the United States (particularly in urban areas) up until the beginning of the 20th century. Over the past few years there has been a slight increase in the numbers of imported cases of cholera in Ireland and in Europe as a whole, due in large part to the greater mobility of people who travel to areas where cholera is endemic.  

Where are you likely to find cholera?
Cholera occurs mainly in poor countries with inadequate sanitation and lack of clean drinking water and in countries at war where the infrastructure of sewerage, water and hospitals may have broken down. 

Can cholera be treated?
Cholera can be very simply treated with replacement fluids and salts, which are lost through diarrhoea. During major epidemics in less developed countries, almost 90% of patients can be completely treated by taking fluids and salts by mouth. More severely ill patients, however, will need to be given fluids intravenously.  

What can you do to protect yourself against cholera?
You are really only at risk from cholera while travelling in less developed countries where the disease is widespread. Even in these countries though, the risks for travellers is very low. The very best way to protect yourself and your family while abroad is to practise good personal and food and water hygiene in endemic areas. Washing hands after using the toilet and before preparing food and before eating or drinking anything is extremely important. An EU licensed oral cholera vaccine has been added to the Irish Medicines Board list of vaccines that are authorised and marketed for use in Ireland.

WHO has issued the following advice for travellers:
By taking a few basic precautions when travelling, cholera as well as most other food and water-borne diseases can easily be prevented. The main rule is: Always be aware of the quality of what you eat and drink when you are travelling

  • Drink only water that has been boiled or disinfected with chlorine, iodine or other suitable products. Products for disinfecting water are generally available in pharmacies. Beverages such as hot tea or coffee, wine, beer, carbonated water or soft drinks, and bottled or packaged fruit juices are also usually safe to drink
  • Avoid ice, unless you are sure that it is made from safe water.
  • Eat food that has been thoroughly cooked and is still hot when served. Cooked food that has been held at room temperature for several hours and served without being reheated can be an important source of infection.
  • Avoid raw seafood and other raw foods, except fruits and vegetables that you have peeled or shelled yourself. Remember: Cook it, peel it, or leave it.
  • Boil unpasteurised milk before drinking it.
  • Ice cream from unreliable sources is frequently contaminated and can cause illness. If in doubt, avoid it.
  • Be sure that meals bought from street vendors are thoroughly cooked in your presence and do not contain any uncooked foods.

If you are travelling with family members or others, ensure that they also take these precautions. Infants under six months who are breast-fed, and receive no other foods or drinks, have a low risk of infection.

What happens if a case appears in Ireland?
Every so often, cases of cholera are imported into Western European countries, including Ireland. Such cases are quickly identified and control measures put in place by Health Board Public Health professionals. These control measures are similar to those for other diarrhoeal illnesses. Contacts of the ill person are identified and screened to outrule any illness. Where the ill person and their contacts work in such areas that have the potential for further spread, they must remain away from work until they are declared safe to return to work. Once these control measures are in place there is little risk of further spread. 

Where can I learn more about cholera?
The following are valuable resources, providing current information on cholera:

European Centre for Disease Prevention and Control

World Health Organization

Centers of Disease Control and Prevention, US

Updated 21st January 2011