The government says Zika infections have been confirmed in nine pregnant women in the United States.
All got the virus overseas. Three babies have been born, one with a brain defect.
The Centers for Disease Control and Prevention said Friday that it is also investigating 10 additional reports of pregnant travelers with Zika.
The Zika virus — spread mainly by mosquito bites — is epidemic in Latin America and the Caribbean. The virus causes mild illness or no symptoms in most people. But in Brazil, officials are investigating a possible link to babies born with brain defects and abnormally small heads.
Of the U.S. pregnancies, two ended in miscarriages and two in abortions. Two pregnancies are continuing without reported complications.