Nine American women who traveled to Zika-affected countries while pregnant have tested positive for the virus, the Centers for Disease Control reported.

Of the nine, one gave birth to an infant with severe microcephaly, an affliction marked by an abnormally small head that scientists think may be linked to the disease.

At least one of two women who terminated their pregnancy did so after brain abnormalities were detected, CDC officials said Friday, while two other pregnancies ended spontaneously in the first trimester. The health agency cautioned that it’s still too soon to say whether Zika caused the birth defects or miscarriages. 

The first official report on Zika among pregnant U.S. travelers adds urgency to warnings last month that pregnant women should delay travel to areas of Latin America and the Caribbean where the mosquito-borne virus is rapidly spreading. Zika is circulating in at least 31 countries and territories in the Americas since it was detected in Brazil in May 2015, according to the World Health Organization. Brazil and French Polynesia are the only countries so far to report increases in microcephaly.

Zika could cost the region $3.5 billion in 2016 through lost travel and tourism, as well as economic and medical costs of the illness, according to an initial estimate the World Bank published Feb. 18. That’s 0.06 percent of the GDP of Latin America and the Caribbean. In recent days, companies from Goldman Sachs Group Inc. to Royal Caribbean Cruises Ltd. to Starwood Hotels & Resorts Worldwide Inc. have added disruption from Zika to the risk factors disclosed to investors in company filings.

The links between Zika and microcephaly or other negative pregnancy outcomes haven’t been definitively established, but “the evidence for this is getting stronger by the day,” CDC Director Tom Frieden told reporters on a conference call. The CDC also reported six cases of women who acquired Zika after having sex with men who were sick with the virus or shortly after their symptoms resolved. “We did not … anticipate that we would see this many sexually transmitted cases of Zika,” Frieden said.

The CDC has advised couples in which men have been exposed to Zika to use condoms or abstain from sex during pregnancy. It’s also published travel advice for pregnant women.

Scientists are conducting studies attempting to confirm the link between catching Zika while pregnant and giving birth to an infant with microcephaly. If the virus does cause the birth defects, officials would expect to see a cluster of microcephaly in Colombia in June, based on the pattern of how Zika spread from Brazil.

Any link between Zika and pregnancy loss would be harder to prove, because it’s a relatively common event. Miscarriages occur during the first trimester in 9 percent to 20 percent pregnancies, according to the CDC. The report noted that a causal relationship between Zika and pregnancy loss hasn’t been established.

All nine women experienced such symptoms of Zika as fever, rash, red eyes, or joint pain. Two gave birth to apparently healthy infants, and two remain pregnant with no known complications, the CDC said.

The CDC is currently investigating 10 other suspected cases of Zika in pregnant women that have not yet been confirmed by lab tests.

This article was written by John Tozzi from Bloomberg and was legally licensed through the NewsCred publisher network.

Tags: health, zika
Photo Credit: Health workers stand in the Sambadrome spraying insecticide to combat the Aedes aegypti mosquito that transmits the Zika virus in Rio de Janeiro, Brazil. Leo Correa / Associated Press