AILSA CHANG, HOST:
An Ebola outbreak in the Democratic Republic of Congo appears to be slowing down, with no new cases in recent weeks. But health authorities fear that a fresh outbreak could emerge because Ebola is one of several viruses that can hide inside the bodies of survivors, sometimes for years. NPR's Gabrielle Emanuel has more.
GABRIELLE EMANUEL, BYLINE: A decade ago, Liberia emerged from a nightmare, an outbreak of Ebola. It had shuttered schools, forced markets to close. Patients unable to find a hospital bed died in the streets. In all, about 5,000 lives were lost. But finally, in early March of 2015, there were no more Ebola cases in the country.
SOKA MOSES: There was so much relief. In fact, at this time, we were tearing down the Ebola treatment center.
EMANUEL: Soka Moses was the medical director for one of those Ebola treatment centers. He says life was returning to normal for the West African country. And then...
MOSES: Boom - a case was identified.
EMANUEL: A new Ebola patient, a middle-aged woman.
MOSES: Everybody was panicking. People say, oh, my God, are we starting this again?
EMANUEL: Part of the panic was the mystery. Where did she get the virus from? There were no other cases around. Eventually, the family pointed medical investigators to the woman's sexual partner. He was Ebola survivor. He'd recovered five months earlier.
MOSES: Just test negative on two different occasions and doing perfectly fine - no symptoms whatsoever.
EMANUEL: Moses says investigators tried to track him down to learn more.
MOSES: First, he was really afraid. He was in hiding. He thought, you know, he was in really big trouble.
EMANUEL: Once he was coaxed out of hiding, scientists started trying to figure out where in his body the virus could be holding on, even after he'd recovered from the disease. They ultimately tested his semen, and that's where they found it.
MOSES: So that was the first documented, sexually transmitted case of Ebola virus disease.
EMANUEL: In addition to semen, there are other places in the body Ebola can hide out.
JOEL MONTGOMERY: A good example is the brain, the eye, the reproductive tissue, like testes.
EMANUEL: Joel Montgomery is at the U.S. Centers for Disease Control and Prevention. He says these are all parts of the body referred to as sanctuary sites.
MONTGOMERY: What is a sanctuary site? So it's an area in the body where the immune response does not get into, simply put.
EMANUEL: There's a lot scientists still don't know, like exactly how long does the virus hide out there? Sometimes it's months. Sometimes it's years. Can it be transmitted to a sexual partner or reinfect the original host? Occasionally, yes, but how often is unknown. Elizabeth Higgs is with the National Institutes of Health.
ELIZABETH HIGGS: I think it's top of the research agenda.
EMANUEL: She says this is a critical issue because these days, medical care has improved so that there are thousands of Ebola survivors, some of whom are harboring the virus and could ignite a new outbreak a month later or even five years later. Higgs says this is exactly how many Ebola outbreaks have started.
HIGGS: Almost all the outbreaks recently have come - maybe not every single one of them, but the vast majority, once we sequence them, are traced back to a previous outbreak.
EMANUEL: Higgs says in many countries, there are survivor programs after an Ebola outbreak, partly to help the recovered Ebola patients who face intense stigma and partly to monitor semen in the survivors to see if the virus is still present. They also educate people about the risk of reinfection and transmitting the virus to a partner. But Higgs says it's a delicate balance.
HIGGS: You don't want to stigmatize the survivors. You know, I would just put the onus on the researchers. Like, come on. Like, you guys need to come up with a solution.
EMANUEL: Especially because it's not just Ebola that can hide out in the body. It's true for other viruses too, like Zika. She says researchers like herself are working to find medications that can reach the viruses that are beyond the reach of the body's immune system.
Gabrielle Emanuel, NPR News. Transcript provided by NPR, Copyright NPR.
NPR transcripts are created on a rush deadline by an NPR contractor. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.