This infection of vectors without a previous blood meal seems to play a role in single, sudden breakouts of the disease.Three epidemiologically different infectious cycles occur in which the virus is transmitted from mosquitoes to humans or other primates. In the "urban cycle", only the yellow fever mosquito A. aegypti is involved. It is well adapted to urban areas, and can also transmit other diseases, including Zika fever, dengue fever, and chikungunya. The urban cycle is responsible for the major outbreaks of yellow fever that occur in Africa. Except for an outbreak in Bolivia in 1999, this urban cycle no longer exists in South America.Besides the urban cycle, both in Africa and South America, a sylvatic cycle (forest or jungle cycle) is present, where Aedes africanus (in Africa) or mosquitoes of the genus Haemagogus and Sabethes (in South America) serve as vectors. In the jungle, the mosquitoes infect mainly nonhuman primates; the disease is mostly asymptomatic in African primates. In South America, the sylvatic cycle is currently the only way humans can become infected, which explains the low incidence of yellow fever cases on the continent. People who become infected in the jungle can carry the virus to urban areas, where A. aegypti acts as a vector. Because of this sylvatic cycle, yellow fever cannot be eradicated except by eradicating the mosquitoes that serve as vectors.In Africa, a third infectious cycle known as "savannah cycle" or intermediate cycle, occurs between the jungle and urban cycles. Different mosquitoes of the genus Aedes are involved.
Eosinopenia is a form of agranulocytosis where the number of eosinophil granulocytes is lower than expected. Leukocytosis with eosinopenia can be a predictor of bacterial infection. It can be induced by stress reactions, Cushings syndrome, or the use of steroids. Pathological causes include burns and acute infections. See also
Eosinophilia
Hypereosinophilia

References
Further reading
Krause JR, Boggs DR (1987). "Search for eosinopenia in hospitalized patients with normal blood leukocyte concentration". Am. J. Hematol. 24 (1): 55–63. doi:10.1002/ajh.2830240108. PMID 3799595. S2CID 20021710. == External links ==