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 called microcephaly, in which the head is smaller than normal and the brain has not developed properly.
Last week, the Centers for Disease Control and Prevention said pregnant women and women of child-bearing age planning to become pregnant should consider postponing trips to outbreak areas including Brazil, Colombia, the Commonwealth of Puerto Rico and 11 other countries and territories.
“We thought it was very important to warn people as soon as possible,” said Dr. Lyle Petersen, director of the CDC's division of vector borne infectious diseases, on a media teleconference last week.
“We are not able to predict how much Zika virus will spread in the U.S."
Scientists haven't yet proved that a Zika virus infection in mothers is causally linked to birth defects in infants, but the CDC still sees an association between the two, leading the center to issue the advisory, Petersen said.
It's possible that the first case of Zika-related microcephaly has already happened in the United States.
On Jan. 15, the Hawaii State Department of Health announced that the mother of the child born with microcephaly "likely had Zika infection when she was residing in Brazil in May 2015 and her newborn acquired the infection in the womb," according to a statement.
According to the CDC, one in five people infected with Zika virus will develop symptoms, which are relatively mild and can include fever, red eyes (conjunctivitis) rash and joint pain.
Brazilian health officials have said that there were more than 3,500 microcephaly cases reported in the country from October 2015 to January 2016, the CDC said.