By Sarah Ferris - 02/05/16 11:50 AM EST
The Centers for Disease Control and Prevention (CDC) said Friday that men with potential exposure to the Zika virus should consider abstaining from sex if their partner is pregnant.
Federal health officials are stepping up their warnings of the virus, which was transmitted sexually in Texas for the first time this week — the first locally transmitted case in the U.S.
While the virus causes mild symptoms in adults, it has been linked to birth defects in babies born to Zika-infected women.
Llittle is known about the link between the virus and a birth defect called microcephaly — something that CDC Director Dr. Tom Frieden said is a priority for national and global research.
“We wish we knew more, we wish we could do more. We know this is anxiety provoking from women who are pregnant and their families,” Frieden said in a conference call with reporters.
He stressed that the situation is "evolving rapidly," adding that a virus has not been linked to a birth abnormality in more than 50 years.
The Zika virus has been rapidly spreading across South America and Central America: The CDC has issued travel warnings for more than 25 countries.
A total of 51 cases have been reported in the U.S., all but one from travel. The number of cases has nearly doubled in the last month.
Twenty cases have also been reported in Puerto Rico, a U.S. territory. Out of those cases, six have been pregnant women and one child has been affected. One other person has been diagnosed with a potentially paralyzing condition called Guillain-Barré syndrome that has been linked to the virus.