Zika virus (ZIKV) is a member of the Flavivirus genus and Flaviviridae family of viruses. ZIKV is an arthropod-borne virus (arbovirus) and is primarily transmitted by mosquitoes. The virus earned its name from the site of its first formal identification in 1947, in the Zika forest in Uganda. ZIKV gained widespread media attention as a result of a major epidemic in 2015 following its introduction into Latin America. Like other flaviviruses, ZIKV contains a genome composed of single stranded positive-sense RNA, which is surrounded by a capsid and a lipid envelope derived from the host cell.
The symptoms of ZIKV infection vary by age. Adults are typically asymptomatic or develop mild symptoms, with the infection lasting around 2 to 7 days. However, ZIKV infection can cause severe congenital defects in the foetus if infection occurs in pregnant women, predominantly microcephaly and other neurological and developmental defects.
Symptoms (in adults) include:
- Joint pain
- Muscle pain
ZIKV is primarily spread by mosquitoes, especially Aedes aegypti and Aedes albopictus. ZIKV can additionally be spread from pregnant women to the foetus via the placenta. ZIKV can also be transmitted through sexual intercourse, blood transfusion and organ transplantation. As well as humans, ZIKV infects some non-human primate species and can reinitiate human transmission cycles from these wild animal reservoirs.
Since ZIKV requires mosquitoes for its major transmission route, the distribution of ZIKV is limited by the presence of its mosquito vectors. The virus is distributed across tropical and subtropical regions of the Americas, Africa and Asia. ZIKV is not endemic in Europe, although isolated instances of local transmission have been observed in some European countries.
Impact for Society – what are we doing?
We are carrying out basic science research into how ZIKV establishes infection in the mosquito vector and what barriers exist that influence the mosquito-borne transmission of ZIKV. ZIKV needs to be able to infect and replicate in both mosquito and human cells; we study the virus in both systems to understand the constraints and requirements for replication in these two different environments. We are also using our fundamental insights into vector-virus interactions to try to create new barriers to transmission, for example virus-resistant mosquitoes. In the longer term this could help us develop new ways of preventing human infection by blocking viral transmission.
Image: A digitally colorised transmission electron microscopic (TEM) image of Zika virus. Virus particles, here colored red, are 40nm in diameter, with an outer envelope, and an inner dense core. Image via CDC/Cynthia Goldsmith.