<< By the late 19th century there were several theories about the cause and transmission of yellow fever, and in 1881 Carlos Juan Finlay of Havana, Cuba, suggested that the infectious agent was transmitted by the mosquito now known as Aedes aegypti. In his investigation of Finlay's theory, Major Walter Reed of the U.S. Army demonstrated in 1900 the transmission of yellow fever from one human to another through the bite of A. aegypti. Reed was further able to show that mosquitoes (rather than bodily contagion, as had previously been thought) were the only vector of the disease. Reed's discoveries were quickly taken up by the American surgeon William Crawford Gorgas, who was able to practically eliminate yellow fever from Havana through the control of the Aedes mosquito. Gorgas' success was repeated in Rio de Janeiro and then in Panama during the building of the Panama Canal. The last outbreak of yellow fever in the United States occurred in 1905, when New Orleans and other ports of the South were invaded.
The yellow-fever patient's convalescence is prolonged, but, when recovery does occur, it is complete and is accompanied by a lifelong immunity. The mortality rate of yellow fever varies greatly, depending upon the strain of virus and, to a certain extent, upon the race of the patient. Many persons may experience only a mild infection that lasts a few days.
There is no specific treatment for those with yellow fever. Good nursing and supportive care, particularly reduction of fever, are important both in maintaining comfort and in reducing mortality.
Yellow fever is an outstanding example of a completely preventable disease. Originally, the control of Aedes aegypti mosquitoes was the only preventive procedure available, as, for example, the campaign against them that made the construction of the Panama Canal possible. Live-virus vaccines, which produce active immunity without clinical illness, are the second great preventive measure.
 >>