Cholera is caused by a bacteria commonly known as vibrio comma. When seen under the microscope, they appear as minute comma organisms. They have 1-2 flagella and are motile. The comma bacillus is gram negative. It grows well in alkaline medium between 30°C-40°C. It does not survive long in water but grows well outside the body in soil and waste materials.

The incubation period varies from a few hours to three days.

The disease is characterized by the onset of acute watery diar­rhoea, vomiting, cramps in the legs and suppression of urine followed by rapid dehydration and great thirst. The stools are thin like rice water and may be accompanied by pain in the stomach. If not controlled in time, the patient may collapse. The infection occurs more in summer and autumn months than in winter. It spreads indirectly through the housefly and carriers. Indiscriminate disposal of waste and lack of personal cleanliness are the other main causes of the disease spreading. Dreadful epidemics are known to have occurred due to sheer carelessness.

The period of communicability varies from 7-14 days. During this period the vibrio comma is present in stools and vomit. An attack of cholera provides immunity for several years. Anti-­cholera inoculations provide immunity and should be taken regularly.