Cholera

What causes cholera?

Cholera is caused by the bacterium Vibrio cholerae, which people swallow in food or water contaminated by the faeces of an infected person. The bacterium produces a toxin in the small intestine that triggers massive watery diarrhoea. It is fundamentally a disease of unsafe water and poor sanitation.

What are the symptoms of cholera?

Most infections are mild or symptomless. In severe cases, symptoms begin within hours to 5 days: profuse, watery 'rice-water' diarrhoea, vomiting, and rapid dehydration. Untreated, severe cholera can kill within hours through fluid loss, low blood pressure and shock. Warning signs of dangerous dehydration include sunken eyes, intense thirst, and reduced skin elasticity.

How is cholera treated?

The cornerstone is rehydration. Oral rehydration solution (ORS) — clean water with salts and sugar — saves about 99% of patients when given promptly. Severe cases need intravenous fluids. Antibiotics (doxycycline, azithromycin) shorten the illness and reduce spread but are secondary to fluids. Oral rehydration therapy is one of the highest-impact medical interventions of the 20th century.

How does cholera spread?

Through the faecal-oral route: ingesting water or food contaminated with the faeces of an infected person. It spreads explosively where sewage mixes with drinking water — refugee camps, slums, areas hit by floods, war or earthquakes. It does not spread by casual person-to-person contact; the route is almost always contaminated water or food.

How many cholera pandemics have there been?

Seven. The first began in 1817 in the Ganges delta. The third (1846–1860) was the deadliest and prompted John Snow's famous 1854 investigation of London's Broad Street pump — a founding moment of modern epidemiology. The seventh pandemic began in 1961 in Indonesia and, remarkably, is still ongoing today, driven by the El Tor biotype.

Is cholera still a problem today?

Yes. The WHO estimates 1.3 to 4 million cases and 21,000 to 143,000 deaths from cholera every year. Major recent outbreaks have hit Haiti (after the 2010 earthquake), Yemen (the largest in recorded history, over 2.5 million suspected cases) and parts of sub-Saharan Africa. It remains entirely a disease of poverty and broken water infrastructure.

Is there a cholera vaccine?

Yes. Oral cholera vaccines (such as Dukoral, Shanchol and Euvichol) give around 65% protection for several years and are used in outbreak response and high-risk areas. They complement — but do not replace — clean water and sanitation, which remain the only permanent solution.

Who was John Snow and why does he matter for cholera?

John Snow was a London physician who, during the 1854 Broad Street outbreak, mapped cholera deaths and traced them to a single contaminated water pump — disproving the prevailing 'bad air' (miasma) theory and demonstrating that cholera spread through water. Removing the pump handle helped end the outbreak. His work is considered the birth of modern epidemiology.