Zika viruses infecting neurons, 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. The zika virus has been shown to replicate in nerve cells. This can lead to microcephaly (small head) in foetuses, which can cause miscarriage or death soon after birth, or lead to developmental delays and disorders. In children and adults it can lead to Guillain-Barre syndrome, which causes rapid-onset muscle weakness.