Zika virus (ZIKV) is a member of the virus family Flaviviridae and the genus Flavivirus.^[3] It is spread by daytime-active Aedes mosquitoes, such as A. aegypti and A. albopictus.^[3] Its name comes from the Zika Forest of Uganda, where the virus was first isolated in 1947.^[4] Zika virus is related to the dengue, yellow fever, Japanese encephalitis, and West Nile viruses.^[4] Since the 1950s, it has been known to occur within a narrow equatorial belt from Africa to Asia. From 2007 to 2016, the virus spread eastward, across the Pacific Ocean to the Americas, leading to the 2015–16 Zika virus epidemic.

The infection, known as Zika fever or Zika virus disease, often causes no or only mild symptoms, similar to a very mild form of dengue fever.^[3] While there is no specific treatment, paracetamol (acetaminophen) and rest may help with the symptoms.^[5] As of 2016, the illness cannot be prevented by medications or vaccines.^[5] Zika can also spread from a pregnant woman to her fetus. This can result in microcephaly, severe brain malformations, and other birth defects.^[6][7] Zika infections in adults may result in temporary paralysis, and rarely in Guillain–Barré syndrome.^[8]

In January 2016, the United States Centers for Disease Control and Prevention (CDC) issued travel guidance on affected countries, including the use of enhanced precautions, and guidelines for pregnant women including considering postponing travel.^[9][10] Other governments or health agencies also issued similar travel warnings,^[11][12][13] while Colombia, the Dominican Republic, Puerto Rico, Ecuador, El Salvador, and Jamaica advised women to postpone getting pregnant until more is known about the risks.^[12][14] Zika is pronounced /ˈziːkə/ or /ˈzɪkə/.^[15][16]