Walter Reed (13 September 1851 – 22 November 1902) was an American physician in the U.S. Army medical corps who is known for his research on the epidemiology of yellow fever, at a time when viruses had only just been discovered.
Reed started to study yellow fever in the USA in the 1890s, showing that walking through swampy woods at night was associated with the disease, while drinking water from the Potomac River was not. In 1900, he led an army commission under the direction of George Miller Sternberg to investigate yellow fever in Cuba, where the disease was endemic. Building on Carlos Finlay's work suggesting that yellow fever was transmitted by a particular species of mosquito acting as a vector, Reed and co-workers confirmed Finlay's results, and also disproved the popular idea that the disease was transmitted by contaminated objects, such as clothing or bedding. The experiments involved the deliberate infection of human volunteers, several of whom died of yellow fever, and Reed pioneered the concept of medical consent.