Brian Foy is seen in 2008 in a Senegalese village wearing a mosquito aspirator and holding a box full of freshly caught mosquitoes. (Kevin Kobylinski/Courtesy of Brian Foy)

For years, it was a curiosity.

Brian Foy, a researcher who studies mosquito-borne diseases, said in a 2011 paper that he had found likely evidence of a little-known virus spreading through sex. If true, it would be the world's first documented case of sexual transmission of the virus, he said at the time.

Foy wanted to study it further, but no one would give him the funding he needed: He had found just one example, and the virus — known as Zika — was too obscure, he was told.

Neither is true anymore.

On Monday, the World Health Organization designated the Zika virus — and its suspected complications in newborns — a public health emergency of international concern.

On Tuesday, health officials in Dallas announced what appeared to be a confirmation of Foy's findings. A resident there was infected with the virus through sex, they reported, prompting the WHO to call for further investigation Wednesday.

(This video was updated on Feb. 2, 2016.) Authorities have confirmed more than 30 cases of Zika virus in the United States. Here's what you need to know. (Gillian Brockell/The Washington Post)

The announcement served as an unfortunate vindication for Foy, who has long sought funding to research the issue.

"We could have had a lot more research done by now, and perhaps an idea that this might be a concern in future epidemics (like our current one) and how to control it," the Colorado State University vector biologist said by email after the Dallas case was confirmed. "Now we all are behind and need to catch up."

Foy was introduced to Zika by chance. And, as with so many revelations, the one at the heart of his 2011 paper arrived over beers.

But first, there was a mystery in need of solving.

In summer 2008, Foy and a then-graduate student, Kevin Kobylinski, were conducting research in the village of Bandafassi, in southeastern Senegal, a region known for transmission of diseases by mosquitoes. Late that August, the duo returned home to northern Colorado and both men promptly got sick.

That came as little surprise.

But then something strange happened.

Days after Foy became ill, his wife, Joy Chilson Foy, came down with similar symptoms: Headaches, chills, wrist pain and torso rashes.

As the sickness spread, Foy did something that might seem odd to anyone but a scientist: He drew and froze samples of their blood and enlisted the help of the Centers for Disease Control and Prevention for further testing.

Because viruses are often undetectable by the time symptoms arise, the CDC scientists looked for antibodies, the body's deployed defense against a virus. The results implicated the Dengue virus in Foy, but they couldn't figure out what his wife had. Stumped, they all moved on with their lives.

In 2009, however, Kobylinski returned to Senegal. There, he got drinks with another scientist, who it so happened was the grandson of one of the men credited with first discovering Zika decades ago.

"I read all of my grandfather's papers, so that stuff really interests me," that researcher, Andrew Haddow, told Science magazine for a 2011 article which first reported on Foy's story — and identified him, his wife and Kobylinski as the anonymous patients in their paper.

Haddow suggested that the trio test their frozen samples for Zika. All three samples tested positive.

"It was clear that she got Zika and I had Zika and so we made the connection that I certainly did transfer it to her," Foy told The Washington Post.

But if that was true, then how? Foy assumed he and Kobylinski were infected by mosquitoes in Senegal. His wife's infection, though, was perplexing.

It couldn't have been a mosquito, because the tropical mosquitoes that transmit Zika probably wouldn't be found in Fort Collins, Colo., certainly not at that time of year. And anyway, the Zika virus has to marinate in a mosquito for about two weeks before it can be transferred again to another human.

It was also unlikely to have been transmitted through direct contact, because that's never been documented for such viruses before — and, besides, Foy's four children remained healthy.

"I wrestle with my kids and kiss them and play with them all the time — especially after being away from them," Foy recalled.

That left him with one conclusion: Zika can be sexually transmitted.

He wrote his paper and got it published in 2011 in the CDC's Emerging Infectious Diseases journal.

But he wanted to know more.

"I started studying it, but very limitedly because I couldn't get funding for it," Foy said. "Nobody would want to fund it — they were like this is a one-off event and Zika isn't important."

Five years later, nobody can say that anymore.

Following the alarming announcement that health officials had discovered a case of sexually transmitted Zika — a "game-changer," according to the Dallas County Health and Human Services director — Foy said he had mixed feelings.

"I'm excited that it seems to be another confirmation of our initial findings," he wrote in an email, "but sad to think of what it might mean for the public and how to control this disease."

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