Zika virus, originally identified in 1947 from the Zika forest of Uganda, is transmitted to people primarily through the bite of an infected Aedes species mosquito. These mosquitoes are found throughout tropical regions of the world and are the same mosquitoes that spread dengue and Chikungunya viruses. Mosquitoes become infected with the Zika virus when they feed on a person already infected with the virus. Infected mosquitoes can then spread the virus to other people through bites. Zika virus can also be spread by sexual intercourse and from mother to child. There is no vaccine to prevent Zika or medicine to treat a Zika virus infection.
Outbreaks of Zika have occurred in Africa, Southeast Asia, and the Pacific Islands. Because the Aedes species mosquitoes are found throughout the world, and, therefore, it is possible that outbreaks will spread to new countries. To date, Zika virus has been reported in several countries and territories in the Americas. Zika has also been linked to serious birth defects, including microcephaly, when contracted by expectant mothers during pregnancy.
The most common symptoms of Zika virus disease are fever, rash, joint pain, and conjunctivitis (redness in the eye) though only 1 in 5 cases is symptomatic. The illness is usually mild with symptoms lasting from several days to a week. Infection is thought to provide lifelong immunity. Severe disease requiring hospitalization is uncommon and deaths are extremely rare. CDC recommends testing people who have 2 or more symptoms with a history of travel to a Zika endemic area; or have 3 or more symptoms if they suspect local transmission; or if a person lives, works, or frequents an area of active, ongoing transmission.