Global: an anatomy of cholera

IRIN answers frequently asked questions about the disease that has killed nearly 3,000 people in its latest large-scale outbreak in Zimbabwe since August 2008.

What is Cholera?

Vibrio cholerae is a rod-shaped bacterium. It has two major biotypes: classic and El Tor. El Tor is the biotype responsible for most of the cholera outbreaks reported from 1961 to the present.

Cholera is a diarrhoeal disease caused by infection of the intestine. In most cases, infection causes only mild diarrhoea or no symptoms at all. In 5 percent to 10 percent of cases, however, patients develop severe watery diarrhoea and vomiting from 6 hours to 5 days after exposure to the bacterium.

The initial symptoms of the disease are queasiness, nausea and abdominal gurgling, followed by acute diarrhoea. The loss of large amounts of fluids can rapidly lead to severe dehydration. In the absence of adequate treatment, death can occur within hours. Those who are malnourished or already have intestinal parasites can be at especially high risk of death.

How did cholera get its name?

The disease's name was coined from the Greek word, Khole, meaning "flow of bile". Cholera's watery diarrhoea is often referred to as "rice-water" stool, as it contains flecks, which are mucus and epithelial cells. The diarrhoea causes victims to lose huge amounts of potassium ions, which can also lead to cardiac complications and circulatory failure.

Where did Cholera originate?

The first known cholera outbreak was recorded in the Indian sub-continent in 1817. Since then at least seven distinct cholera pandemics have been recorded, the first six from the Ganges Delta, viewed as the "ancestral home" of the disease.

How did cholera travel to other parts of the world?

It is thought that cholera was inadvertently transported from India to the shores of the colonial power, Britain, in the bilge water of English ships. The contaminated water was dumped on arrival at home ports, and the disease moved rapidly to Europe and then to Russia. Emigrants to the New World were thought to have taken the disease to the Americas.

In 1832 a cholera epidemic swept through New York, killing 3,515 of the city's then population of 250,000.

In 1991 a Chinese registered freighter discharged bilge water into a Peruvian harbour, sparking a cholera pandemic that affected 322,562 people after a nearly 100-year hiatus of the disease in South America.

By 1994 there were more than 1 million cases recorded in South America.
In the aftermath of the Rwandan genocide in July 1994, cholera struck Goma's refugee camps in the neighbouring Democratic Republic of Congo. There were about 70,000 cases and 12,000 deaths.

How is cholera spread?

A Ukrainian parliamentarian remarked during a 1994 outbreak of the disease in his country that "the spread of cholera and other infectious diseases is the calling card of an economy in trouble."

The spread of cholera and other infectious diseases is the calling card of an economy in troubleCholera infects humans through the consumption of infected water or contaminated food. The consumption of raw or poorly cooked seafood, raw fruit and vegetables, and other foods contaminated during preparation or storage can lead to infection. Bacteria present in the faeces of those infected are the main source of contamination. The bacterium can also survive in brackish rivers and coastal waters. The disease spreads rapidly where sewage and drinking water supplies are inadequately treated.

When was the disease identified?

British doctor and epidemiology pioneer John Snow, and Robert Koch from Germany, the 1905 Nobel Prize recipient for Physiology or Medicine, are credited with unlocking the mysteries of cholera.

In 1831 England experienced its first cholera outbreak, where the disease was attributed to "miasma [pollutants] in the atmosphere". Another outbreak occurred in 1854 and on 31 August the London district of Soho suffered what Snow was later to call "the most terrible outbreak of cholera which ever occurred in the kingdom."

Within three days 127 people living close to Soho's Broad Street succumbed to the disease; by 10 September 500 had died and nearly three-quarters of the residents had fled their homes.

Snow suspected cholera was a waterborne disease and zeroed in on the Broad Street pump which served the area. He convinced the authorities to close the pump down and immediately deaths in the area were rapidly reduced.

Can cholera be prevented?

Yes. People living in high-risk areas can protect themselves with good hygiene and safe food preparation, such as washing their hands before preparing food and eating, by thoroughly cooking food and eating it while it is hot, by boiling or treating drinking water, and using sanitary facilities.

The simple rule is: boil it, cook it, peel it, or forget it.

What treatments are available?

The most important treatment is rehydration, which consists of prompt replacement of the water and salts lost through severe diarrhoea and vomiting. Early rehydration can save the lives of nearly all cholera patients. Most can be rehydrated quickly and easily by drinking large quantities of a solution of oral rehydration salts. Patients who become severely dehydrated may need to receive fluid intravenously.

Packets of oral rehydration salts are available from most city pharmacies and health care facilities. If you have diarrhoea - especially severe diarrhoea - and are in an area where there is cholera, seek treatment immediately from a physician or other trained health care provider. Begin drinking water and other non-sweetened fluids, such as soup, on the way to getting medical treatment.

Sources: World Health Organisation, MedicalEcology.org, University of California, Los Angeles Department of Epidemiology, International Public Health and Human Rights in the Developing World (A Case Study in Peru), Tropical infectious diseases, principals, pathogens and practice.

Article courtesy of www.irinnews.org