Ebola virus can exist in the semen of male survivors of the disease for at least nine months after their initial infection appears, much longer than previously thought, scientists said.


In preliminary results that raised questions about how and when the epidemic might be brought to an end, researchers said they did not know if the traces of virus that were discovered were live or potentially infectious.


"These results come at a critically important time, reminding us that while Ebola case numbers continue to plummet


‘’ Ebola survivors and their families continue to struggle with the effects of the disease," said Bruce Aylward, a World Health Organisation (WHO) Ebola expert.


Aylward said survivors, of whom there are up to 17,000 in West Africa, needed "continued, substantial support for the next six to 12 months to meet these challenges and to ensure their partners are not exposed to potential virus."


Ebola infected 28,000 people and killed more than 11,300 in an outbreak centred in Guinea, Sierra Leone and Liberia that is just coming under control.


Disease experts said they are only now able to learn more about Ebola and its potential longer-term effects on survivors.


Jonathan Ball, a molecular virology professor at Britain's Nottingham University, said Wednesday's findings were worrying.


"This confirms that Ebola virus can persist in the genital tract for a considerable length of time, months after the virus has disappeared from the blood,’’


‘’It worryingly shows that this long-lived reservoir is a potential source of new infections," Ball said in a statement.


The research included 93 male Ebola survivors over age 18 from Freetown, who gave semen samples for testing, the men enrolled in the study two to 10 months after their illness began.


All of the men, who were tested in the first three months after becoming ill, were positive for Ebola virus.


Some 65 percent tested four to six months after their illness were positive, while a quarter of those tested seven to nine months after falling ill tested positive.


The researchers in a statement about their results said that “why some study participants had cleared the fragments of Ebola virus from semen earlier, others remain unclear."


It said further tests of the samples were being conducted by the U.S. Centres for Disease Control and Prevention "to determine if the virus is live and potentially infectious."


Meanwhile, the WHO has advised all male survivors to test three months after the onset of symptoms and then monthly until they know they have no risk of passing on the virus.


"Until a male Ebola survivor's semen has twice tested negative, he should abstain from all types of sex or use condoms when engaging in sexual activity," WHO said in a statement.


The need to washed hands after any physical contact with semen was also stressed