Zika is a largely mosquito-borne virus which while often mild in itself, can cause neurological and auto-immune complications.

Zika is spread mostly by Aedes mosquitos active during the day, but also by infected men to their partners during sexual activity. Those infected with Zika usually experience no symptoms, although one in five may have mild headaches, fever and joint pain.

Unborn babies are particularly at risk from Zika, as infection in pregnant women can cause neonatal microcephaly (impaired brain growth and head size, linked to intellectual impairment and seizures) and other central nervous system (CNS) malformations.

The World Health Organization (WHO) declared Zika virus a health emergency in February 2016. Ten countries have reported neonatal CNS malformations associated with maternal Zika virus.

First identified in Uganda in 1947, Zika has spread rapidly since 2007 and has now been identified in more than 60 countries. Forty-six of these countries were Zika-free before 2015.

The risk of ZIKV infection has been estimated to be larger in South America than in any other part of the world. Four million Zika infections were predicted for 2016 in the Americas alone. In January 2016, Brazil had 99.7 reported cases of microcephaly per 100,000 live births, compared to 5.7 per 100,000 in 2010. A third of these cases have been confirmed as linked to Zika. Other outcomes associated with Zika infection in utero may involve miscarriages and stillbirths.

The virus has also been linked to an increase in cases of auto-immune disease Guillain-Barré syndrome.

Burnet laboratories are in the process of receiving isolates of the Zika virus, with research plans for these underway. Zika has recently been reported in PNG, and Burnet Institute is well placed to monitor its spread and identify populations at risk through its Healthy Mothers Healthy Babies program in East New Britain.

More than 40 Zika vaccine candidates are in the pipeline and 5 are entering Phase I trials.

The social and economic cost of the recent spread of the Zika virus in Latin America and the Caribbean was estimated at US$7-18 billion between 2015 and 2017. This comprised direct outlays, lost productivity, loss from death and the impact of avoidance.

Infections by Dengue virus, a related virus transmitted by the same mosquitoes, are thought to have cost USD$8.9 billion to the global economy in 2013.

Pregnant women are advised to avoid travel to countries known to be infected with Zika if possible, or to take measures to avoid mosquito bites.