Health officials are investigating 14 new reports of Zika virus infections in the United States. The cases are suspected to have been sexually transmitted.
The U.S. Centers for Disease Control and Prevention (CDC) made the announcement Tuesday. It said all of the 14 cases are women. Their only known risk was sexual contact with a male partner who had recently returned from an area where Zika is found.
Some of the cases involve pregnant women. Scientists have found evidence of a link between the Zika virus and microcephaly. Babies with microcephaly are born with unusually small heads and can suffer developmental delays. But scientists have not proven a certain cause and effect.
The CDC researchers said the new cases suggest that sexual transmission of Zika may be more common than they had thought.
The first case of Zika virus transmission in the United States was reported in Texas in early February. Health officials confirmed that it was contracted through sex and not a mosquito bite.
Although sexual transmission of Zika is possible, health officials said that the main cause of Zika is still from mosquito bites. They urged people to prevent mosquito bites by using mosquito repellent, wearing long-sleeved shirts, and using window screens.
CDC had an advisement for men who have recently traveled to areas with Zika. They advised using condoms or avoiding sexual contact with pregnant women or women who could become pregnant.
At least 29 countries in the Americas have experienced Zika outbreaks. The World Health Organization has declared the spread of Zika a global health emergency.
On Tuesday, the CDC added two more countries, Trinidad and Tobago and the Marshall Islands, to its Zika virus travel advisory.
