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Genome analysis shows Ebola can be sexually transmitted

19 October 2015
Appeared in BioNews 824

Traces of Ebola virus RNA have been found in the semen of survivors up to nine months after infection, genome analysis has revealed. Although it is not known if the traces come from a live virus, a second report suggests Ebola could be sexually transmitted.

It was previously thought that Ebola remained in bodily fluids for only three months after infection but results from the genetic analysis of semen samples taken from 93 Ebola survivors showed that, six months after infection, 65 percent of men still had traces of virus RNA in their semen, as did 24 percent after nine months.

Testing on a sample taken from a man ten months after infection was inconclusive. It is not known if the traces were from intact versions of the virus, which could be passed on, or from fragments of an inactive virus, explains NHS Choices.

The researchers also found that the amount of Ebola RNA present in the semen decreased over time, but it is not known how this affects virus infectiousness.

'The study is limited by sample size but does demonstrate concerning findings - that viral genetic material is present in semen for up to nine months following onset of symptoms of Ebola virus infection,' said Dr Nathalie MacDermott, from Imperial College London, who was not involved in the study. 'Of note the authors have yet to determine if live, and therefore infectious, virus is present in these samples.'

A second report, published concurrently in the NEJM, states that Ebola had been sexually transmitted to a woman six months after her partner had been infected.

The Liberian woman, who died seven days after diagnosis, had reported that two weeks previously she had unprotected sexual intercourse with a man who had previously been infected Ebola in September 2014. The man provided blood and semen samples for testing, which when compared to the genome of the woman showed signs consistent with direct transmission.

Other cases of sexual transmission have been reported, but this is the first to be scientifically investigated.

Professor Jeremy Farrar, director of the Wellcome Trust, who was not involved with the studies, said: 'The fact that there has so far been only one isolated [official] report of this type of infection suggests that this kind of  transmission may be rare, but it highlights just how much we still don’t understand about the Ebola virus, infection and recovery'.

There are currently around 16,000 survivors of Ebola in Western Africa. 

Ebola lingers in semen for nine months
BBC News |  14 October 2015
Ebola RNA Persistence in Semen of Ebola Virus Disease Survivors - Preliminary Report
New England Journal of Medicine |  14 October 2015
Ebola survivors can carry virus in their sperm 'for nine months'
The Guardian |  14 October 2015
Is Ebola an STI? Virus can survive in semen for up to nine months
NHS Choices |  15 October 2015
Molecular Evidence of Sexual Transmission of Ebola Virus
New England Journal of Medicine |  14 October 2015
Persistent virus in people recovering from Ebola virus disease
World Health Organisation (press release) |  14 October 2015
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