A new study has found that the Ebola virus could persist in the semen of male Ebola survivors for at least nine months since they got infected, a lot longer than scientists initially thought. This finding has given rise to new questions about how long the potential risk of exposure could be, according to the World Health Organization.

The study, which was funded by WHO and jointly conducted by the Sierra Leone Ministry of Health and Sanitation, the U.S. Centers for Disease Control and Prevention and the WHO, followed 93 male Ebola survivors in Sierra Leone who were tested for the virus at different intervals.

Those who were tested within the first three months of their infection all tested positive for Ebola. However, between the fourth and sixth month of infection, only 65 percent were positive, and between the seventh to ninth month, only 24 percent were positive. The risk appeared to decline over time.

In one participant, the virus was found nine-and-a-half months since the onset of the virus. The researchers have not yet determined how long the virus could actually persist in semen.

"We think there is a potential risk of exposure but we cannot determine that with 100 percent certainty right now," study co-author Dr. Nathalie Broutet of WHO told ABC News.

"We do not yet have data on the extent to which positivity on RT-PCR is associated with virus infectivity," the authors of the study wrote. "Although cases of suspected sexual transmission of Ebola have been reported, they are rare; hence the risk of sexual transmission of the Ebola virus is being investigated."

WHO recommended that male Ebola survivors be tested for the virus three months after infection. Those who would test positive at three months should be tested twice every month, with one-week intervals between the two tests, until they test negative. While their tests remain positive, they should abstain from sex, WHO said.  

The study was published in the Oct. 14 issue of the New England Journal of Medicine.