Zika virus (ZIKV) is a flavivirus that results in either asymptomatic infection or mild disease. It was first identified in Uganda in 1947 and sporadic cases of disease were reported in Africa and Asia. It is transmitted by mosquitoes of the genus Aedes. Sexual transmission of ZIKV is rare but has been documented.
In 2007 ZIKV was recorded outside Africa and Asia for the first time: an outbreak occurred on Yap Island in the Federated States of Micronesia. It was during a subsequent outbreak in 2013-14 in French Polynesia that the first cases of possible perinatal transmission and Gullain-Barré syndrome were reported. In 2014 and 2015, further outbreaks in the Pacific Islands occurred.
In 2015 to 2016, ZIKV spread throughout South and Central America, the Caribbean and parts of North America. Due to an increase in microcephaly and developmental defects in newborn children being noted in the outbreak a Public Health Emergency of International Concern (PHEIC) was declared by the World Health Organisation (WHO) between February and November 2016. The PHEIC has now been replaced by the WHO's longer term Zika Strategic Response Plan.
Since 2016, ZIKV infection in pregnancy has been established as the cause of Congenital Zika syndrome which may have severe and fatal consequences for the fetus.