Over the past year, the Zika virus, an arthropod-borne Flavivirus, has transitioned from a relatively unknown tropical disease to the cause of a public health emergency. The Zika virus is transmitted by the Aedes species of mosquito as well as by sexual intercourse. Although the symptoms of acute Zika virus infection are usually mild and self-limited, it causes fetal microcephaly in pregnant women, and is associated with an increased risk of Guillain-Barré syndrome. The risk of microcephaly from Zika virus infection is estimated to be highest in women who are infected during the first trimester of pregnancy. The Zika virus has been shown to have significant neurotrophism in vivo and in vitro, although further study is needed to characterize its mechanisms of pathogenesis. Zika virus has previously caused two known outbreaks in the Pacific region prior to the current epidemic in South and Central America, and the current epidemic has affected at least 440,000 to 1,300,000 people. The population of the vector for the current epidemic, Aedes aegypti, varies seasonally in the United States, however there have been few documented cases of local spread of the Zika infection in the United States and it is unclear whether epidemic spread of Zika will occur within the United States.
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