Although symptoms associated with Zika virus are generally mild, a possible association has been observed between the unusual rise of Zika cases and microcephaly cases in Brazil since 2015.

What is microcephaly?

Microcephaly is a condition where a baby is born with a small head or the head stops growing after birth. Microcephaly is usually a rare condition, with one baby in several thousand being born with the birth defect. If this combines with poor brain growth, babies with microcephaly can have developmental disabilities.

The most reliable way to assess whether a baby has microcephaly is to measure head circumference 24 hours after birth, compare this with the World Health Organisation (WHO) growth standards, and continue to measure the rate of head growth in early infancy.

Brazil has reported an unusual, sudden increase in babies born with microcephaly since May 2015.

Prevention

Mosquitoes and their breeding sites pose a significant risk factor for Zika virus infection. Prevention and control relies on reducing mosquitoes through source reduction (removal and modification of breeding sites) and reducing contact between mosquitoes and people.

This can be done by using insect repellent; wearing clothes (preferably light-coloured) that cover as much of the body as possible; using physical barriers such as screens, closed doors and windows; and sleeping under mosquito nets.

It is also important to empty, clean or cover containers that can hold water such as buckets, flower pots or tyres, so that places where mosquitoes can breed are removed.

Special attention and help should be given to those who may not be able to protect themselves adequately, such as young children, the sick or elderly.

During outbreaks, health authorities may advise that spraying of insecticides be carried out. Insecticides recommended by the WHO Pesticide Evaluation Scheme may also be used as larvicides to treat relatively large water containers.

Travellers should take the basic precautions described above to protect themselves from mosquito bites.

Women who are pregnant or planning to become pregnant should take extra care to protect themselves from the bites of the mosquito that transmits Zika.