Zika virus (ZIKV) was first discovered in 1947 in the Zika Forest of Uganda. Shortly thereafter, it was isolated from mosquitoes in the area and then humans in 1968. ZIKV is a flavivirus similar to yellow fever, dengue, Japanese encephalitis, and West Nile virus (WNV). The disease had only been detected in central Africa and throughout Southeast Asia until associated with a diesease outbreak on Yap Island, in the South Pacific in 2007. From there, it spread to South America with human cases first reported in 2014.
ZIKV does not appear to require an animal reservoir, like WNV, which is perhaps a factor in the rapid spread throughout the Americas. Non-infected mosquitoes are able to acquire the virus after feeding directly on infected humans. Without a "middle man" in the endemic cycle of ZIKV, the virus can spread quite rapidly where abundant, competent vector mosquitoes and humans are present together. Today, there is active transmission of the virus throughout South and Central America and the Caribbean Islands. Please refer to Figure 1 in VDCI's Zika Virus Fact Sheet.