Today is the birthday of Walter Reed, an American medical researcher born in 1851 who is celebrated for his work on yellow fever. During the Spanish-American War, more soldiers had died from the disease than in combat. So in 1900, Major Reed, who was a professor at the Army Medical School, led a four-person Commission of the United States Army on yellow fever in Havana, Cuba. The commission confirmed that yellow fever, like malaria, was transmitted by mosquitoes. A scientist on the commission allowed himself to be bitten, suffered several days of high fever, and died.
Further experiments on soldier volunteers produced 22 cases of experimental fever: 14 from mosquito bites, six from injections of blood, and two from injections of filtered serum. Those results suggested that the disease organism was not a bacterium, but rather a nonfilterable organism, now known as a virus. Yellow fever was then eradicated by destroying mosquito breeding grounds.
[Source: Trevor I. Williams, Ed., A Biographical Dictionary of Scientists (John Wiley & Sons, New York, ed. 3, 1982).]