DDT, or dichlorodiphenyltrichloroethane, was recognized as a potential pesticide in 1939 by the Swiss chemist Paul Muller. It was first widely used during World War II and thereafter throughout the world to combat yellow fever, typhus, elephantiasis, and other diseases carried by insects. DDT helped reduce the number of malaria cases worldwide and increased crop and livestock yields in developing countries. It came under scrutiny with the 1962 publication of Silent Spring, a book in which American marine biologist Rachel Carson asserted that DDT was destroying other animal life by entering the food chain. The United States banned DDT in 1972 except for in cases of extreme health emergencies. Many other nations also have banned it or placed it under strict control.