Zika virus causes a serious birth defect called microcephaly — an underdeveloped brain and small head — and is linked other neurological disorders in adults. Roughly 4 in 5 infected people are asymptomatic, but its most common symptoms are mild and include fever, rash, joint pain and red eyes.

The virus is primarily spread through mosquito bites and can also be transmitted through sex and blood transfusions.

A public health emergency of international concern was declared by the World Health Organization on Feb. 1 as the virus spread through Latin America and the Caribbean. Women who are pregnant or thinking of becoming pregnant are advised to not travel to Zika-affected areas

The CDC has confirmed Zika virus causes microcephaly and other severe fetal brain defects. It can be passed from a pregnant woman to her fetus during pregnancy or at delivery. The agency advises women who are pregnant or thinking of becoming pregnant to not travel to Zika-affected areas.

If a pregnant woman’s male partner has been to such an area, the couple should abstain from sex or use condoms during the pregnancy. Currently, the CDC does not believe there is risk for the future pregnancies of a woman who has Zika once the virus clears from her blood.