Dr. Craig Spencer, who volunteered in Guinea with the humanitarian organization Doctors Without Borders, tested positive for the Ebola virus on Thursday. For the days he was symptomless, he went about his daily life. Spencer visited a coffee stand at the High Line, took a three-mile run on Riverside Drive, went bowling and traveled by subway.

Spencer -- who was admitted to Bellevue Hospital Center in New York City with a fever of 103 degrees after experiencing no symptoms until Thursday morning -- may have even had sex with his fiancée, Morgan Dixon. But can Ebola spread through semen?

While Ebola is known to spread through bodily fluids including urine, saliva, sweat, feces, vomit and blood -- semen can also put a person at risk -- but it’s “extremely, extremely, extremely, extremely unlikely,” Dr. Daniel G. Bausch of the Tulane University School of Public Health and Tropical Medicine told the New York Times.

Dr. William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University Medical Center in Nashville, Tennessee, agrees. "Of all the modes of transmission, that's going to be the last," Schaffner told Live Science. "It's a little like asking me, 'If we're all going to go from New York to San Francisco, will one of us walk?' That doesn't happen too often."

When Ebola symptoms -- including high fever, vomiting, diarrhea and bleeding -- are present, it’s unlikely an individual will be up for sex, Schaffner said.

Still, the Centers for Disease Control and Prevention wants Ebola patients to air on the side of caution. “Abstinence from sex (including oral sex) is recommended for at least 3 months. If abstinence is not possible, condoms may help prevent the spread of disease,” the CDC writes in its recommendations.

According to the World Health Organization, men who have recovered from the disease can still transmit the virus through their semen for up to seven weeks after they have been cured. The CDC says the virus can still be found in male survivors up to 101 days after the onset of symptoms. A lab worker who contracted Ebola still had traces of Ebola in his semen 61 days after he recovered, according to the WHO.

More than 4,800 people have died in the Ebola epidemic that began in March. The vast majority of cases are in the three West African countries: Guinea, Liberia and Sierra Leone.