NEW YORK — A sexually transmitted case of Zika in Texas has scientists scrambling to understand how much of a risk infection through sex is.

Experts stress that mosquitoes are still the main culprit in the Zika epidemic menacing Latin America and looming over the United States. ‘‘Mosquitoes would be the great river of transmission, while sexual transmission is going to be akin to a mountain stream,’’ said Dr. William Schaffner, an infectious disease expert at Vanderbilt University.

But the Texas case has spurred discussion about ways in which Zika and other illnesses, commonly thought to be carried only by mosquitoes, might be spread. Other types of transmission can be hard to spot amid outbreaks in which many mosquito-borne infections are occurring, said Dr. Ali Khan, a former disease investigator for the Centers for Disease Control and Prevention. ‘‘It’s very hard to parse this out in the middle of an epidemic,’’ said Khan, now dean of the University of Nebraska’s college of public health.

Discerning something like sexual transmission would have to occur in a place where an outbreak was not raging, he said. That’s what happened in Dallas.

The Zika epidemic is on track to cause millions of infections in Latin America and the Caribbean, but no transmission was reported in the United States until the Dallas case this week.

Health officials said a person there — who had not traveled to an outbreak area — was infected. An investigation concluded the person caught the virus through sex with a person who had recently returned from Venezuela, where Zika infections have been growing.

Officials released few details about the case, except to say both patients have recovered. But it wasn’t the first to raise the possibility of sexual transmission of the virus.

A Colorado State University researcher, Brian Foy, picked up the virus in Africa and apparently spread it to his wife back home in 2008. More recently, it was found in a man’s semen in Tahiti.

With the Dallas case, ‘‘we’re all kind of scrambling in the scientific community how best to tackle this and how best to research it,’’ said Foy.

Most people infected with Zika experience, at the most, only mild symptoms. But mounting evidence in Brazil has suggested a connection between the virus and babies born with brain defects and abnormally small heads.

World Health Organization spokesman Tarik Jasarevic said the Texas case is ‘‘obviously a concern. We need to know more about how likely this is to happen.’’