Ebola outbreak in West Africa may not get suppressed as there is still a higher risk of transmission via the semen of male survivors than previously thought.
The World Health Organization's advice is that all male survivors should be tested three months after the onset of symptoms and then monthly until they know they have no risk of passing on the virus through their semen, said Bruce Aylward, head of the WHO's Ebola response.
But a forthcoming study in the New England Journal of Medicine
, based on around 200 survivors, found that around half still had traces of the virus in their semen after six months, said a clinician.
"The old advice of three months is no longer good. The number of people with persistent virus in their semen is much greater than expected," he added.
"It's not the sex that is dangerous, it's the semen that is dangerous. How people actually get exposed, in soiled linens or whatever, is not clear," said Aylward.
Transmission through semen may explain why a few cases continue to occur even though the outbreak has been almost completely eradicated by an intense international effort, recently bolstered by the deployment of a trial vaccine in Guinea and Sierra Leone.
The latest flare-up, in a village on the northern border of Sierra Leone, followed the death of a 67-year-old woman late last month, 50 days after the previous confirmed case in the region. Transmission chains are considered to have been broken after 42 days with no new infections.
However, Aylward said that sexual transmission was "obviously not a huge risk, because if it were we would have seen a lot more in the areas that were hardest hit at the beginning of this outbreak."