On this day, 123 years ago, February 22, 1902 (January 15, 1902 in the lunar calendar), scientists found that yellow fever was transmitted by mosquitoes. On February 22, 1902, Colonel Walter Reid and Dr. James Carroll of the U.S. Army Yellow Fever Research Commission in Cuba issued a scientific report reporting that yellow fever, a terrible tropical epidemic, was transmitted by mosquitoes. More importantly, at the initiative of the committee, the city of Havana has developed a plan to completely eradicate mosquitoes to help eradicate yellow fever in this densely populated area. Cuban doctor Carlos J. Finlay once told Reid, chairman of the Yellow Fever Research Council, that he believed yellow fever was spread by Aedes aegypti. The committee later tested this assumption. However, the price paid in this work was heavy-Dr. Razir was bitten by a mosquito carrying the virus and unfortunately died in the line of duty. In the report, the committee also said that the incredible pathogen carried into the bloodstream by mosquitoes can pass through thin porcelain filters and is smaller than any known bacterium. This pathogen may be invisible to ordinary microscopy, and scientists call this kind of pathogen a viral virus. Walter Reed, Medical Doctor