The problem of jungle yellow fever in Brazil becomes relatively more important with the effective control of Aedes aegypti in all urban centers and its eradication from large sections of the country. Indeed, among the 1,258 liver specimens collected by the Viscerotomy Service from January of 1932 to June of 1945, on which the diagnosis of yellow fever was made, only 78 came from localities where A. aegypti still existed. The remainder (1,180) were derived from rural areas where, presumably, the infection was acquired through the bite of some forestbreeding mosquito. Moreover, this epidemiological variety of the disease is not only significant in being responsible for an overwhelming proportion of human infections in recent years, but also in constituting uncontrolled foci of the virus.
The transmission of yellow fever by sylvan mosquitoes was suspected by Lutz (1) in 1929, but convincing proof that human infection may occur in the absence of A. aegypti was not forthcoming until a few years later when Soper et al (2) investigated a rural epidemic in Valle do Chanaan, State of Espirito Santo.