Sex and Ebola: How risky?

When Dr. Craig Spencer went to volunteer in West Africa with the humanitarian organization Doctors Without Borders, it took him far away from his home, family, friends and other people he loves, including his fiancé Morgan Dixon. Once he returned, Doctors Without Borders advised that he should monitor his health for signs of illness like running a fever, but that "as long as a returned staff member does not experience any symptoms, normal life can proceed."

"Normal life" may presumably include sexual activity -- but could that put a person's partner at risk?

On Thursday, after Spencer tested positive for the Ebola virus, health officials announced that Dixon, along with two friends, had been quarantined so their health can be monitored.

Ebola is transmitted through bodily fluids, but only after a patient begins showing symptoms, experts say. Even though sex involves a high level of bodily fluid exchange -- including semen, saliva and sweat -- most experts say it isn't risky if a person is not showing initial flu-like symptoms of the virus such as a high fever, body aches and vomiting or diarrhea. It's safe to say that such symptoms could compel a person to crawl into bed -- but most likely alone.

In that way Ebola is different from other viruses, such as HIV and human papillomavirus (HPV), which can spread through sexual contact even when the person has no visible signs of an infection.

But some experts say there still isn't enough information about the transmission of this particular strain of the virus, known as Ebola Zaire.

It is still uncertain how quickly the virus emerges in a various bodily fluids and at what level. A study published in 2007 in the Journal of Infectious Diseases tried to answer this question by analyzing a variety of samples taken from patients during an Ebola outbreak in Uganda that occurred in 2000. The Ebola virus was detected in 8 of 16 saliva samples and 1 of 2 semen samples. Those samples were taken when the patients already had serious, acute infections. It's unclear how much of the virus might be present earlier in a patient's illness.

However, health experts say there is definitely reason to be concerned about sex after Ebola. Research conducted over the years has found that Ebola does remain in a patient's semen for much longer than other bodily fluids, even after a patient has recovered from the acute infection and it's no longer detectable in a blood test.

According to the World Health Organization, a lab worker who contracted Ebola on the job was found to have traces of the virus in his semen 61 days after the initial infection. Subsequent research has found the virus can live for up to three months in semen. This could theoretically mean a man could infect his partner weeks or even months after he has recovered from the illness.

This research has prompted the U.S. Centers for Disease Control and Prevention to encourage abstinence for three months after recovering from Ebola. Or failing that, the health agency strongly recommends condom use.