Zika virus particles infecting a cell (yellow), computer illustration. Zika virus is an RNA (ribonucleic acid) virus from the Flaviviridae family. It is transmitted to humans by Aedes sp. mosquitoes. The virus infects skin cells and spreads to the bloodstream. It causes zika fever, a mild disease with symptoms including rash and joint pain. In 2015 a previously unknown connection between Zika infection in pregnant women and microcephaly (small head) in newborns was reported. This condition can cause miscarriage or death soon after birth, or lead to developmental disorders.