During the Spanish-American War in 1898, the U.S. Army forces were hit with massive casualties due to Yellow-fever. Medical professionals did not know how the illness was transmitted. After the war members of the U.S. Army Yellow Fever Commission, headed by Walter Reed, traveled to Cuba. The mission was to study the disease and determine how it is transmitted. Initial studies pointed suggested that a living host was needed due to the incubation period of 10 to 17 days. Commission members’ decided to test Cuban physician Carlos Finaly’s mosquito-vector theory that he proposed in 1881.
American physician and committee member, Jesse Lazear tested this theory by hatching mosquito eggs and allowing them to feed on patients with Yellow fever. The mosquito then fed on volunteers over a period of two weeks, no infections resulted. However the mosquitoes fed again two days later and the volunteers fell ill with the disease. This proved that mosquitoes, specifically the Aedes aegypti variety, were the transmission vector of yellow fever. The two volunteers exposed recovered, however Lazear was not as fortunate. He contracted yellow fever and died in September 1900. In 1901 Clara Maass, a volunteer nurse, and two Spanish immigrants also perished from these tests. These deaths caused a public outcry and immediate cessation of yellow fever experiments in Cuba.
The research by the commission determined the time period (12-20 days) in which the mosquito could infect another human. They also determined that after infection, a victim would typically fall ill within six days. Reed’s research on yellow fever was instrumental in the fight against yellow fever. He is also credited with using the first type of medical consent during these experiments in Cuba.
After the Spanish-American War William C. Gorgas was promoted to Chief Sanitary Officer in Havana. Gorgas took the research from Walter Reed and the U.S. Army Yellow Fever Commission and was able to eradicate yellow fever and malaria in the area. Gorgas achieved this by implementing far-reaching sanitary programs. These programs included draining of ponds and swamps, fumigation, mosquito netting, and construction of public water systems. Within a year cases in Havana dropped from 784 to zero.