Discovery of Yellow Fever Transmission

In 1900 and 1901 a United States Army commission led by Walter Reed confirmed the theory, first proposed by the Cuban physician Carlos Finlay, that yellow fever is spread by the bite of a particular species of mosquito rather than through direct contact with the sick or with contaminated clothing and bedding. The commission's conclusions were established through deliberate, and by later standards ethically troubling, experiments in which volunteers allowed themselves to be bitten by mosquitoes that had fed on yellow fever patients. Once the mosquito's role was confirmed, mosquito control measures brought the disease under control quickly enough to allow the resumption of construction on the Panama Canal, a project earlier crippled by losses to malaria and yellow fever.