This item has been corrected.
Though 35 new cases of Ebola have been reported last week in Guinea and Sierra Leone, the worst of the epidemic is over. Survivors, who become immune to the virus, have been a precious resource in helping treat patients, both by donating blood and working in the Ebola wards. But they also remain contagious with the virus lingering in two areas: the internal chambers of the eye, and semen of male victims. It’s difficult for antibodies to reach these areas.
The virus inside the eye—which has led some survivors to progressive blindness—isn’t shed out through tears, so it’s hardly a vehicle of contagion. Unprotected sex, on the other hand, can cause the spread of the disease. Fortunately, compared to other STDs such as HIV or Hepatitis B, Ebola is harder to transmit through sexual contact, and also has a relatively short life as an STD, with the virus believed to linger in semen for about three months.
“We’ve only had a few anecdotal experiences of sexual transmission,” Daniel Bausch, professor of tropical medicine at Tulane University in New Orleans, told Quartz. Currently, the public health protocol is to recommend abstinence from sex or use of condoms for three months after recovering from the disease. The lack of verified cases of contagion through semen makes it hard to be certain that these guidelines are sufficient. (Research has found that it’s likely not possible to grow the virus in vaginal fluids while the opposite is true for semen.)
The challenge, said Bausch, is not only because of the rarity of sexual transmission, but because even when it’s suspected, it’s hard to verify semen was actually the means of transmission. Now that the rhythm of contagion has slowed down, Bausch said, it’s easier to identify cases.
One such suspected case is a man in Liberia who would have transmitted the virus sexually 82 days after recovery, and whose semen has tested positive for live Ebola virus; that would make it twice the current window of time for which semen is believed to carry the virus. The case hasn’t been verified yet, though even if it were, Bausch said, “it would perhaps be premature to revise the public health guidelines relative to sexual transmission.” This also because, he notes, it’s particularly hard to control people’s sexual behavior.
It is still unclear how long the virus can survive in a patient’s eye. Live Ebola virus has been found 14 weeks after recovery, but the research on how long the virus survives in the body is at its early stages, since this is the first large, widely observed, epidemic.
But human to human contagion—sexual or otherwise—is not likely to lead to another epidemics, said Bausch: The harder variable to control is reinfection from the wild, since animals can be vehicles of the virus.
Correction: The latest cases reported are in Guinea and Sierra Leone.