Dr. Brian Foy of Colorado State University on a research trip to Senegal in 2008. Foy contracted the Zika virus on the trip, which led to a discovery about the disease. 

(Photo courtesy Brian Foy)

Zika has been transmitted in Texas through sexual contact according to a report out Tuesday from the Dallas County health officials. It's the first confirmed instance of the virus spreading within the U.S. 

Until now, experts had focused on mosquitos as the way Zika moves from person to person. Dr. Brian Foy, a professor of vector biology at Colorado State University, is an exception. He suspected that Zika could be sexually transmitted way back in 2008. 

The reason? Foy thinks that he gave his wife Zika after he contracted the disease on a research trip to Senegal.

"We think it was direct contact, and probably think it was sexually transmission," he said on Colorado Matters. "We laid this out in an article in 2011."

Foy eliminated other ways his wife could have gotten the virus. The mosquito that spreads the disease doesn't live in Colorado. And Foy's four kids stayed healthy even after he played with them on his return. That ruled out saliva or physical contact. 

His theory came well before Zika exploded across Latin America and the Caribbean last year. Public health officials worry the rapid spread of the virus could explain the spike in babies born with shrunken heads and undeveloped brains. 

The suspected link is the reason Brazil, Columbia, Jamaica and other countries now advises all women to delay pregnancy by two years. 

The CDC had confirmed 31 cases of Zika in the U.S. as of last Thursday. But in each, a traveler had gotten the disease overseas. The sexual transmission in Texas is the first confirmed spread of Zika within the U.S. 

Foy says it's nice to see his work vindicated, but he worries what the news could mean for current the current outbreak.

"The findings from Dallas seems to confirm our discovery, which is exciting to the scientist in me, but concerning for the general public and for how difficult it may be to control this pandemic. "

He also isn't sure how proof of sexual transmission could change the response to Zika.

"If [sexual transmission] happens at more than a very, very low rate, it could change the epidemiology and the pathology," he said. "Maybe it changes the frequency of the disease of women, maybe it has something to do with some of these unusual pathologies of babies with birth defects." 

For now, the CDC wants people in the U.S. to play it safe. The agency recommends that men should wear condoms after traveling to areas where Zika is common. It also asks women to avoid contact with semen from men recently exposed to the virus. 

The CDC says it plans to issue further guidance soon.