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How did Walter Reed and James Carroll demonstrate how yellow fever spreads?
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In 1900, a U.S. Army commission led by Walter Reed and including James Carroll conducted rigorous experiments in Cuba to determine how yellow fever was transmitted.
Challenging the prevailing belief that the disease spread through contact with contaminated clothing or bedding (fomites), the team investigated the theory of insect transmission originally proposed by Carlos Juan Finlay. Their demonstration involved several key steps:
- Controlled Exposure: On August 27, 1900, James Carroll allowed an infected mosquito to feed on him, subsequently developing a severe case of yellow fever.
- Human Trials: In November 1900, the commission established a controlled camp where they performed experiments on volunteers. They proved that the disease was transmitted by the bite of the Aedes aegypti mosquito.
- Blood Transmission: They further demonstrated that the disease could be induced by injecting blood drawn from an infected patient into a healthy volunteer.
- Exclusion of Fomites: The team found no evidence that the disease spread through fomites, confirming that houses only became infectious in the presence of infected mosquitoes.12