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Typhus fever is a disease that previously caused widespread loss of life during epidemics, especially in connection with wars and disasters. After it was established that several diseases, including malaria, were spread by insects, suspicions arose that this might also be the case with typhus fever. Charles Nicolle noticed that sick people ceased to infect others when they had an opportunity to keep themselves clean. In 1909 he demonstrated that body lice spread typhus fever by successfully transferring the infection among apes by allowing a body louse to first bite infected and then uninfected apes.