It was in 1899 that Dr. Walter Reed was sent to
the US Army garrison just outside Havana, Cuba, to study yellow fever. American soldiers there, as well as Cuban civilians, were dying of the dreaded disease. A variety of theories as to what caused it existed but the principal one was that it was a contagious disease that was spread through contact with yellow fever patients, their clothes and bedding.

During the summer of 1900 Dr. Reed, heading up a team of Cuban and American physicians, began investigating each case but their efforts accomplished nothing. Then something happened for the first time since Reed's arrival in Cuba: a soldier in the US Army prison died of yellow fever. There were nine prisoners in the same room but nothing happened to the other eight. Dr. Reed came to the conclusion that some insect had entered the prison through an unscreened window and bitten the man who died. But what kind of insect?

One of the Cuban doctors mentioned Dr. Carlos Juan Finlay, a Cuban physician who had been investigating the cause of yellow fever for many years. His conviction was that the guilty insect was the Stegomyia mosquito.

Dr. Reed went to see Finlay and after listening to his explanation was convinced that he was right. At the same time he recognized that the Cuban doctor's theory had to be tested and proved.
Two small wooden huts were built. Hut number one was very dirty and contained clothes and bedding of men who had died of yellow fever. The little house was maintained hot and humid. Three volunteers were to remain in the hut for twenty days.

In hut number two, which was antiseptically clean, two volunteers entered. Reed explained to the men in the first hut that in twenty days they would emerge free of yellow fever. In the second hut a Stegomyia mosquito woul be allowed to bite one of the two men. That man, said Reed, would catch yellow fever but with alert staff members at hand he would not catch yellow fever.

Everything went exactly as Dr. Reed predicted. Dr. Finlay's theory had proved to be the correct one!
Immediately a team of soldiers went all over Havana fumigating the houses and street until every Stegomyia mosquito in the city had been exterminated. For the first time in 300 years there was not one case of yellow fever in the city!