Zika virus (ZIKV) is a member of the Flaviviridae virus family and the flavivirus genus. In humans, it causes a disease known as Zika fever. It is related to dengue, yellow fever, West Nile and Japanese encephalitis, viruses that are also members of the virus family Flaviviridae.

Along with other viruses in this family, Zika virus is enveloped and icosahedral with a non-segmented, +ssRNA genome. It is most closely related to the Spondweni virus and is one of the two viruses in the Spondweni virus clade. The virus was first isolated in 1947 from a rhesus monkey in the Zika Forest of Uganda, Africa and was isolated for the first time from humans in 1968 in Nigeria. From 1951 through 1981, evidence of human infection was reported from other African countries such as Uganda, Tanzania, Egypt, Central African Republic, Sierra Leone and Gabon, as well as in parts of Asia including India, Malaysia, the Philippines, Thailand, Vietnam and Indonesia. It is transmitted by mosquitoes and has been isolated from a number of species in the genus Aedes - Aedes aegypti, Aedes africanus, Aedes apicoargenteus, Aedes furcifer, Aedes luteocephalus and Aedes vitattus. Studies show that the extrinsic incubation period in mosquitoes is about 10 days. The vertebrate hosts of the virus include monkeys and humans.