[Transmission and conservation of the amaril virus in nature]

The yellow fever virus is a monkey Flavivirus transmitted by mosquitoes. The transmission cycles and vectors vary from Western to Eastern Africa and in South America. There are two types of endemic areas where the virus is maintained: humid forests and emerging zones and areas where intermediary and urban epidemics occur. On both continents, the virus circulates in forest areas by moving epizooties from one region to another among non immune monkeys. The virus can also be maintained in an enzootic or epidemic zone by vertical transmission from a female to her offspring. This type of transmission was proven experimentally as early as 1903 by Marchoux and Simond for Aedes aegypti, the urban vector of yellow fever, but was observed in nature only in 1995. However, the isolation of the virus in male Ae. furcifer taylori in 1977 in Senegal had already suggested that this kind of transmission took place in nature. The vertical transmission of the yellow fever virus means that it can survive, from one rainy season to the next, in Aedes eggs and thus increases the number of contaminating meals and the proportion of females apt to transmit since they infect at a younger age.