In 1873, a German graduate student first synthesized DDT, but it was not used as an insecticide until entomologist Dr. Paul Mueller rediscovered the substance in 1939. DDT was so effectual against flies, mosquitoes, and fleas that it was widely employed during World War II to combat typhus, malaria, and other insect-borne illnesses. The great success of the insecticide resulted in the awarding of the Nobel Prize in medicine to Dr. Mueller in 1948.