Zika viruses infecting human embryo, computer illustration. This is an RNA (ribonucleic acid) virus from the Flaviviridae family. It is transmitted to humans via the bite of an infected Aedes sp. mosquito. It causes zika fever, a mild disease with symptoms including rash, joint pain and conjunctivitis. In 2015 a previously unknown connection between Zika infection in pregnant women and microcephaly (small head) in newborns was reported. This can cause miscarriage or death soon after birth, or lead to developmental delays and disorders.