Zika virus, cut-away molecular model. The virus is surrounded by a lipid bilayer envelope (white), that has proteins (outer red, yellow and black) embedded in it. Inside the envelope is a nucleopcapsid (inner yellow and red) that surrounds the RNA (ribonucleic acid) genome (not seen). This is a 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.