(Bloomberg) -- Nine American women who traveled to Zika-affectedcountries while pregnant have tested positive for the virus,the Centers for DiseaseControl reported. Of the nine, one gave birth to an infant withsevere microcephaly, an affliction marked by an abnormallysmall head that scientists think may be linked to thedisease.

At least one of two women who terminated their pregnancy did soafter brain abnormalities were detected, CDC officials said Friday,while two other pregnancies ended spontaneously in the firsttrimester. The health agency cautioned that it's still too soon tosay whether Zika caused the birth defects ormiscarriages.

Pregnant women should delay travel to areas of LatinAmerica and the Caribbean

The first official report on Zika among pregnant U.S. travelersadds urgency to warnings last month that pregnant women shoulddelay travel to areas of Latin America and the Caribbean where themosquito-borne virus is rapidly spreading. Zika is circulating inat least 31 countries and territories in the Americas since it wasdetected in Brazil in May 2015, according to the World Health Organization. Brazil and FrenchPolynesia are the only countries so far to report increases inmicrocephaly.

Lost travel and tourism

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

The links between Zika and microcephaly or other negativepregnancy outcomes haven't been definitively established, but "theevidence for this is getting stronger by the day,” CDC Director TomFrieden told reporters on a conference call. The CDC alsoreported six cases of women who acquired Zika after having sex withmen who were sick with the virus or shortly after their symptomsresolved. “We did not … anticipate that we would see this manysexually transmitted cases of Zika,” Frieden said.

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

Scientific studies underway

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

Any link between Zika and pregnancy loss would be harder toprove, because it’s a relatively common event. Miscarriages occurduring the first trimester in 9% to 20% pregnancies, according tothe CDC. The report noted that a causal relationship between Zikaand 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 healthyinfants, and two remain pregnant with no known complications, theCDC said.

The CDC is currently investigating 10 other suspected cases ofZika in pregnant women that have not yet been confirmed by labtests.

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