Portal:Viruses/Selected article/21

Zika fever is caused by the Zika virus, a mosquito-borne flavivirus first isolated in Uganda in 1947. Human infection is usually asymptomatic; a minority of cases have mild symptoms, which generally last 2–7 days and can include fever, conjunctivitis, joint pain, headache and a maculopapular rash. Infections in adults have occasionally been associated with Guillain–Barré syndrome. The incubation period is probably up to a week. The natural reservoir is unknown. The virus is transmitted by Aedes mosquitoes, mainly Aedes aegypti in tropical regions. During pregnancy, mother-to-child transmission can cause microcephaly (pictured) and other brain malformations in some babies. In one study, major abnormalities were seen in 42% of live births. The virus is present in semen and male-to-female sexual transmission has been documented; it is also found in breast milk and blood.

The first documented human outbreak occurred in 2007 in the Federated States of Micronesia. The virus is thought to have entered the Americas in around 2013, and an outbreak started in Brazil in 2015, spreading across the Americas and to Pacific, Asia and Africa, and leading the World Health Organization to consider Zika a Public Health Emergency of International Concern in February–November 2016. No specific treatment nor vaccine has been approved. Prevention involves mosquito control and condom use; women in areas where Zika was circulating were recommended to consider delaying pregnancy, and pregnant women were advised to avoid travel to affected areas.