By Steve Tawa

PHILADELPHIA (CBS) — Caribbean travel is often a topic of conversation at this point in the winter, but the Zika Virus has also entered the equation. Many doctors are fielding calls, especially from expectant mothers, who recently traveled to the warm climate countries named on a CDC list.

So far, the federal Centers for Disease Control and Prevention guidelines only recommend blood tests for pregnant women who have gone to areas in which the Zika virus transmission is ongoing.

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“The tests that would be done would depend on whether the patient was having symptoms that are associated with a Zika infection,” says Dr. Kathleen Squires, Director of the Division of Infectious Diseases at Jefferson University Hospital.

But Zika produces no symptoms in 80% of cases. Doctors say pregnant women who visited those countries who show no symptoms should get an ultrasound to screen for fetal infection. The experts say screening women who visited or lived in affected countries during the outbreak period could “flood the CDC,” and it was not feasible.

There is no vaccine or cure.

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Dr. Squires says complex, long-term studies are underway to assess the virus.

‘The CDC is working vigorously with a number of medical groups in Brazil and other areas in the Caribbean,” she says, “as well as in Central and South America to establish these long term studies.”

U.S. health officials have a travel advisory to about 15 countries in the Caribbean, six in Central America, nearly ten in South America, as well as Mexico, where infection has been confirmed from the mosquito-borne Zika virus.

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The CDC says it continues to evaluate all available evidence, and it will update recommendations as new information becomes available.