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Walter Reed,  (born Sept. 13, 1851, Belroi, Va., U.S.—died Nov. 22, 1902, Washington, D.C.), U.S. Army pathologist and bacteriologist who led the experiments that proved that yellow fever is transmitted by the bite of a mosquito. The Walter Reed Hospital, Washington, D.C., was named in his honour.





During most of the 19th century it had been widely held that yellow fever was spread by fomites—i.e., articles such as bedding and clothing that had been used by a yellow-fever patient. As late as 1898, a U.S. official report ascribed the spread to this cause. Meanwhile, other methods of transmission had been suggested. In 1881 the Cuban physician and epidemiologist Carlos Juan Finlay began to formulate a theory of insect transmission. In succeeding years he maintained and developed the theory but did not succeed in proving it. In 1896 an Italian bacteriologist, Giuseppe Sanarelli, claimed that he had isolated from yellow-fever patients an organism he called Bacillus icteroides. The U.S. Army now appointed Reed and army physician James Carroll to investigate Sanarelli’s bacillus. It also sent Aristides Agramonte, an assistant surgeon in the U.S. Army, to investigate the yellow-fever cases in Cuba. Agramonte isolated Sanarelli’s bacillus not only from one-third of the yellow-fever patients but also from persons suffering from other diseases. Reed and Carroll published their first report in April 1899 and in February 1900 submitted a complete report for publication. It showed that Sanarelli’s bacillus belonged to the group of the hog-cholera bacillus and was in yellow fever a secondary invader.

Before this report had actually been published, an outbreak of yellow fever occurred in the U.S. garrison at Havana, and a commission was appointed to investigate it. The members of the commission were Reed, who was to act as chairman, Carroll, Agramonte, and a bacteriologist, Jesse W. Lazear. In the summer of 1900, when the commission investigated an outbreak of what had been diagnosed as malaria in barracks 200 miles (300 kilometres) from Havana, Reed found that the disease was actually yellow fever. Of the nine prisoners in the prison cell of the post, one contracted yellow fever and died, but none of the other eight was affected. Reed and his colleagues thought it possible that this patient, and only he, might have been bitten by some insect. Reed therefore decided that the main work of the commission would be to prove or disprove the agency of an insect intermediate host.

On August 27, 1900, an infected mosquito was allowed to feed on Carroll, and he developed a severe attack of yellow fever. Shortly afterward Lazear was bitten, developed yellow fever, and died. In November 1900 a small hutted camp was established, and controlled experiments were performed on volunteers. Reed proved that an attack of yellow fever was caused by the bite of an infected mosquito, Stegomyia fasciata (later renamed Aedes aegypti) and that the same result could be obtained by injecting into a volunteer blood drawn from a patient suffering from yellow fever. Reed found no evidence that yellow fever could be conveyed by fomites, and he showed that a house became infected only by the presence of infected mosquitoes. In February 1901 official action in Cuba was begun by U.S. military engineers under Major W.C. Gorgas on the basis of Reed’s findings, and within 90 days Havana was freed from yellow fever.


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