U.S. health officials have new guidance for doctors whose pregnant patients may have traveled to regions with a tropical illness linked to birth defects.

Officials say doctors should ask pregnant women about their travel and certain symptoms, and — if warranted — test them for an infection with the Zika (ZEE'-ka) virus.

The virus is spread through mosquito bites, and there have been outbreaks in parts of the Caribbean and Latin America. In Brazil, there's mounting evidence linking the infection to a birth defect in which the head is smaller than normal and the brain has not developed properly.

The Centers for Disease Control and Prevention released the advice Tuesday. Last week, it said pregnant women should consider postponing trips to outbreak areas.