Cholera variants are constantly evolving and need to be monitored closely to prevent outbreaks, say researchers.

A particularly infectious strain of cholera, predicted to lead to an eighth pandemic of the disease, fizzled out after it suddenly became susceptible to antibiotics, but researchers are calling for close monitoring of the bug to prevent future outbreaks.

Cholera, an acute diarrhea disease which spreads through contaminated food and water, first emerged in the Ganges delta in 1817. Seven subsequent cholera pandemics killed millions of people across all continents.

Linked to poor access to clean water and sanitation, the disease typically affects vulnerable communities such as refugees. There are an estimated 1.3 to 4 million infections each year, according to the WHO, and estimates for the number of deaths vary between 21,000 and 143,000, but the true burden is unknown as many cases go unreported.