By Tina Rosenberg
Cholera is on the rise around the world. Last year, according to Unicef, West and Central Africa had “one of the worst ever” cholera outbreaks. An outbreak in Haiti sickened 1 in 20 Haitians and killed more than 7,000 people. The World Health Organization estimates that there are between three million and five million cases of cholera each year, and between 100,000 and 120,000 deaths. New and more virulent strains are emerging in Asia and Africa, and the W.H.O. says that global warming creates even more hospitable conditions for the disease.