Health officials now think Ebola survivors can spread the disease through unprotected sex nearly twice as long as previously believed.
Scientists thought the Ebola virus could remain in semen for about three months. But a recent case in West Africa suggests infection through sex can happen more than five months later.
Based on the case, officials are now telling male Ebola survivors to avoid unprotected sex indefinitely.
They had previously advised using condoms for at least three months.
A report released Friday detailed the case of a 44-year-old Liberian woman whose infection likely came from a 46-year-old man who had Ebola symptoms last September.
She fell ill in March, a week after sex with him, and died. Another woman he had sex with around the same time tested negative.
The Ebola virus spreads through direct contact with an Ebola patient's blood or other bodily fluids like urine, saliva, semen and sweat.
Once patients recover, health officials say they aren't contagious except there's a chance it could still be in semen.
Investigations of other recent Ebola cases in Liberia, Guinea and Sierra Leone have pointed to sexual transmission from survivors, but those have not been confirmed, according to the U.S. Centers for Disease Control.
There have been fewer than 10 such cases, said CDC spokeswoman Kristen Nordlund. It's been difficult to pinpoint that sex was the only way they may have been infected, she added.
In Guinea, Dr. Sakoba Keita, the national coordinator for Ebola response, said a woman in the southeastern town of Macenta contracted Ebola after having unprotected sex with her husband.
For the past month, officials have recommended all survivors use condoms until more is known.