How did U.S. health measures reduce malaria and yellow fever during canal construction?

During the construction of the Panama Canal, U.S. health officials successfully reduced the prevalence of malaria and yellow fever by implementing rigorous mosquito control measures.12

Building on the discovery that mosquitoes were the primary vectors for these diseases, U.S. Army surgeon William Crawford Gorgas was appointed chief sanitary officer in 1904. Drawing on his previous success in Havana, Gorgas focused on eliminating the breeding grounds of the Aedes aegypti mosquito and other species responsible for transmission. By controlling these mosquito populations, the medical staff was able to eradicate yellow fever from the Canal Zone within two years and bring malaria under effective control. These sanitation efforts were critical, as they removed the primary health obstacles that had previously caused massive loss of life during the earlier French construction attempts.1324