Chapter 9 : Zika Virus Disease
Category: Bacterial Pathogenesis; Clinical Microbiology
Zika virus, a flavivirus, is an example of an emerging virus infection ( 1 – 6 ). The virus was first isolated in the Zika Forest, Uganda, in 1947 during a program on yellow fever research. Rhesus monkeys were housed as sentinel animals in cages in the rain forest. When one of the animals developed fever, a filterable and mouse-pathogenic flavivirus, closely related to the yellow fever virus but not identical, was isolated from its blood. Mosquitoes (Aedes [Stegomyia] africana) trapped in the area were found to carry the virus. In tests with experimentally infected mosquitoes feeding on mice and on a monkey, Zika virus was successfully transmitted ( 2 , 7 , 8 ). Zika virus infection is endemic in many regions of sub-Saharan Africa and in South Asia ( 9 – 20 ). Jungle, or sylvatic, transmission cycles serve as the virus reservoir ( 12 , 13 , 17 , 20 ). Infections with Zika virus are asymptomatic in approximately 80% of cases and cause only mild illness, if any, in endemic regions ( 10 – 12 , 18 , 20 , 21 ). Upon importation to the Americas, where Zika virus had not been previously reported, the virus caused outbreaks of mostly asymptomatic mild illness, as in Africa and Asia ( 3 , 4 , 22 ). The difference between “endemic” transmission in the Old World and “epidemic” transmission in Brazil is the occurrence of prenatal infections with serious malformations in cases when the mother had Zika virus disease during the first trimester of gestation ( 3 ).
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