Via The Conversation: How El Niño forecasts can help prevent cholera deaths in Africa. Excerpt:
Since it first emerged from the Ganges River delta 200 years ago, cholera has killed tens of millions of people around the world. It causes acute diarrhea that can kill quickly without proper treatment. Before the 1970s it was not unusual for healthy adults to die of dehydration within days of infection, despite drinking large amounts of water.
By some estimates, over a billion people worldwide live in areas where there is risk of cholera, and hundreds of thousands die every year. But when people have access to clean water, appropriate treatment or vaccine, the risk of cholera is greatly reduced. With well-trained medical staff and supplies, appropriate and timely treatment of cholera patients can ensure that almost no one dies.
In a recent study, our group sought to understand how weather changes caused by El Niño impact cholera risk in Africa, where most cholera deaths occur. El Niño events can now be forecast as much as a year in advance, so knowing this relationship may help forecast where cholera outbreaks are most likely to occur.
We found that major shifts occurred in El Niño years, with more cholera cases occurring in areas where rainfall increased. This kind of advance warning can help health officials plan and have appropriate resources at the ready, thereby preventing substantial numbers of cholera deaths.
Focus on drinking water
People become infected with cholera when they ingest the Vibrio cholerae bacteria, usually from contaminated food or water. By increasing the chances that people will consume contaminated food or water, weather patterns can change cholera risk in several ways.
One of the main ways that cholera can get into water supplies is through the feces of infected individuals. Heavy rains sometimes trigger flooding, causing sewers or latrines to overflow and introducing cholera into otherwise clean water supplies. Conversely, in drier areas where people depend on shallow wells or rain-catching cisterns for their clean water, drought can dry up these supplies and force people to drink from unsafe sources.
Finally, some researchers have found a relationship between sea surface temperature and water salinity and cholera risk. Warmer sea surface temperatures can favor the growth and survival of V. cholerae in coastal waters, increasing the likelihood of a cholera outbreak if the pathogen is introduced into the population via coastal water supplies or contaminated seafood.
Changes in the weather may affect cholera risk via any of these three pathways. This means it is essential to understand local conditions in order to project where cholera outbreaks may occur.
