Climate Link to Cholera Affirmed in New Study in Africa

A study of cholera outbreaks in Zanzibar from 1999 to 2008 has found that moderate increases in ocean temperatures and rainfall can increase the likelihood of cholera epidemics. The study, published in the American Journal of Tropical Medicine and Hygiene, found that a sea surface temperature increase of 1 degree C can lead to a doubling of cholera cases over four months and that moderate increases in rainfall can increase the incidence of cholera cases by 1.6 times. The study said a key reason for the spread of cholera outbreaks is that as ocean temperatures rise, copepods — sea organisms that carry the cholera bacteria — proliferate. Heavier rains also facilitate the spread of cholera by increasing the likelihood that cholera-contaminated seawater will spread inland to towns and villages. The study’s lead author, Mohammed Ali of the International Vaccine Institute in Seoul, Korea, said that governments could use these environmental cues to step up vaccination efforts in cholera-prone areas. A growing number of scientists contend that cholera outbreaks are related to climate and that rising air and ocean temperatures will lead to increased outbreaks of the deadly disease, which sickened more than 220,000 people in 2009.