Dallas County says the CDC confirmed it was transmitted through sexual contact.
The Dallas County Health and Human Services said Tuesday that the first Zika virus case acquired through sexual contact was confirmed by the Centers for Disease Control. The patient was infected after having sex with an ill individual who contracted the virus after traveling abroad.
“Now that we know Zika virus can be transmitted through sex, this increases our awareness campaign in educating the public about protecting themselves and others,” Zachary Thompson, DCHHS director, said in a release.
The CDC didn’t immediately respond to Fortune’s request for comment. Fortune will update this post when CDC responds.
Six Texans have been diagnosed with Zika virus so far, all of whom contracted the disease outside of the U.S. The virus has been linked to possible birth defects. County officials have been regularly setting mosquito traps to test for the Zika virus, and no local mosquitos have been found positive.
There’s only a few cases that suggest Zika was transmitted through sexual contact, and only two studies in the medical literature have hinted that such a method of spreading is possible. In one case, the Zika virus was isolated in semen. In another, a researcher contracted Zika abroad and passed it on to his wife when he returned.
Evidence of Zika being passed via sex is still limited, and the CDC hasn’t issued any warning about the risk, yet.
DCHHS still warns local residents to use caution. “Next to abstinence, condoms are the best prevention method against any sexually-transmitted infections.”