Ebola virus persists and may be transmitted in survivors’ semen, studies show

Ebola virus RNA persists in men’s semen after their recovery from Ebola virus disease, preliminary results from a study in Sierra Leone have shown,1 and a case study has reported a suspected case of sexual transmission of the disease from a male survivor to his female partner earlier this year.2

The Ebola persistence study, published in the New England Journal of Medicine,1 enrolled a convenience sample of 100 men who had survived Ebola virus disease in Sierra Leone. Researchers followed them at intervals after their recovery and collected semen samples in addition to self reported information on their health status.

Results showed that half of the men who provided an initial semen sample for analysis (46 of 93; 49%) had RNA for Ebola virus in their semen at baseline when they were first recruited to the study.

The number of men testing positive for Ebola virus in semen decreased with time after the onset of Ebola virus disease, but rates remained high for as long as nine months after their initial illness.

All of the nine men who gave semen specimens within two to three months of becoming ill with Ebola virus disease tested positive for Ebola virus RNA in their semen.

Two thirds of the men (26 of 40; 65%) who gave semen samples four to six months after disease onset showed the presence of Ebola virus RNA. And just over a quarter of study participants (11 of 43; 26%) who provided semen specimens at seven to nine months after disease onset tested positive. Results from one man who gave a specimen at 10 months were indeterminate.

“These data showed the persistence of Ebola virus RNA in semen and declining persistence with increasing months since the onset of Ebola virus disease,” said the researchers, led by Gibrilla Deen, director of clinical studies at Connaught Hospital in Freetown, Sierra Leone.

They did not yet have data on whether having Ebola virus RNA in the semen was associated with virus infectiveness. Cases of suspected sexual transmission of Ebola have been reported, they said, adding that this route of transmission was now being investigated further.

A case study reported in the same issue of the New England Journal of Medicine2 described a suspected case of sexual transmission based on genomic sequencing data. Ebola virus genomes in blood samples taken from a female patient in Liberia and a semen sample from her male sexual partner were consistent with direct transmission.

The genomes shared three substitutions that were absent from all other western African Ebola virus sequences that have been tested previously and were distinct from the last documented case in the transmission chain in Liberia.

“Combined with epidemiologic data, the genomic analysis provides evidence of sexual transmission of Ebola virus,” said the researchers, led by Gustavo Palacios, director of the Center for Genome Sciences at the US Army Medical Research Institute of Infectious Diseases in Frederick, Maryland, USA. They added that their data provided evidence that infective Ebola virus can persist in semen for 179 days or more after the onset of Ebola virus disease.