Zika infections have been confirmed in nine pregnant women in the United States, including one who gave birth to a baby with a rare birth defect, health officials said on Friday.
The Centres for Disease Control and Prevention said it's investigating 10 more reports of pregnant travellers with Zika. All got the virus while visiting or living in places with Zika outbreaks.
The US cases add to reports out of Brazil. Officials there are exploring a possible link to babies born with unusually small heads, a rare birth defect called microcephaly, which can signal underlying brain damage.
Zika has become epidemic in Latin America and the Caribbean since last fall. The virus, mainly spread through mosquito bites, causes mild illness or no symptoms in most people.
Since August, the CDC has tested 257 pregnant women for Zika; eight were positive, and a state lab confirmed a ninth.
Three of the women have delivered babies; two of the newborns are apparently healthy, and one was born with microcephaly.
Two had miscarriages, but it's unknown if the Zika infection was the cause.
Two women had abortions, one after scans showed the fetus had an undeveloped brain. Details were not provided for the second case.
Two pregnancies are continuing with no reported complications.
Five of the women had Zika symptoms in the first trimester, including the miscarriages, abortions and newborn with microcephaly.
In its report Friday, the CDC did not give the women's hometowns; state health officials have said there were two pregnant women with Zika in Illinois, three in Florida and one in Hawaii, who gave birth to a baby with microcephaly. That mother had lived in Brazil early in her pregnancy.
The CDC said all are US residents, but it declined to answer a question on their citizenship.
The health agency said the nine women had been to places with Zika outbreaks American Samoa, Brazil, El Salvador, Guatemala, Haiti, Honduras, Mexico, Puerto Rico and Samoa.
Those destinations are among the 30 places now on the CDC's travel alert. It recommends that pregnant women postpone trips to those areas.
While the link between Zika and the birth defect has not been confirmed, the possibility has prompted health officials to take cautionary steps to protect fetuses.
The CDC has set up a voluntary registry to collect information about Zika-infected women and their babies.Officials also have made Zika a reportable disease.
Research also is underway into a possible link between Zika and a paralyzing condition in adults called Guillain-Barre.
The CDC on Friday also updated its investigation into 14 cases of possible sexual transmission of Zika from male travellers to their sex partners in the United States. Two cases have been confirmed, four more are probable and two have been dropped, the report said.
Zika is primarily spread by mosquito bites, and transmission through sex was thought to be extremely rare. It's been surprising that this many instances appear to have happened in the United States, CDC Director Dr. Tom Frieden noted during a call with reporters.
Similarly, the number of US cases involving evidence of microcephaly or brain abnormalities "is greater than we would have expected," said the CDC's Dr. Denise Jamieson.
So far, 107 travel-related Zika infections have been diagnosed in 24 states and the District of Columbia, including the pregnant woman.