MINNEAPOLIS (WCCO) — More than a dozen American women may have caught the Zika virus through sex.

On Tuesday, the U.S. Centers for Disease Control (CDC) said all 14 possible cases involve men who visited countries experiencing outbreaks.

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Those men likely got infected by mosquitos then passed the virus on to partners during sex. Two of the women are pregnant. The virus could be causing birth defects.

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So the CDC now advises men who’ve traveled to outbreak areas to use condoms or abstain from sex with pregnant women.

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Destinations like Mexico, Jamaica and Puerto Rico are considered countries with active Zika transmission. You can see the full list at the CDC’s website.