Evidence Confirms Ebola Persists in Semen for 6 Months

It was suspected earlier this year that an Ebola survivor in Liberia sexually transmitted the virus to a woman, and now that has been confirmed.

Although there had not been any new cases of Ebola in 30 days, the woman tested positive in March 2015. It was then discovered that she had sexual contact with a male Ebola survivor who tested negative for the virus in October 2014. Investigators from the United States Army Medical Research Institute of Infectious Diseases (USAMRIID) looked deeper into this case and found molecular proof of sexual transmission.

After the male patient died on March 27 doctors obtained a semen sample. The low levels of viral RNA required an alternative method for evaluation.

“We implemented a new enrichment strategy in collaboration with scientists from Illumina, Inc. that was pivotal in obtaining the required coverage to complete downstream genomic analysis,” Michael Wiley, PhD, of USAMRIID, said in a news release.

The next-generation sequencing involved extracting Ebola RNA from the semen and comparing it to a blood sample from the female patient. Sure enough the samples were consistent with direct transmission.

“The samples shared three genetic substitutions that have not been found in any other Ebola virus sequences in Western Africa,” described Jason Ladner, PhD, of USAMRIID. The changes were different from the previous transmission chain in Liberia. Taking this into consideration along with epidemiological data, all signs pointed to sexual transmission.

As detailed in The New England Journal of Medicine, the virus remained infective in semen for 179 days or longer after onset of the disease. Testes are among the list of organs that are ‘immune privileged,’ Mariano Sanchez-Lockhart, PhD, of USAMRIID, explained.

“Within these sites, viruses might evade systemic immune responses and persist longer since the ‘immune pressure’ is more restricted than systemically,” she said.

This discovery is a step in the right direction on multiple paths. For one, it could help design effective treatments which target the immune privileged sites. It also shows the importance of real-time diagnostics, especially for large disease outbreaks.

“This work allowed for more informed decisions about how to manage and control the spread of the disease. To be in the field, during an outbreak, and have the ability to make near real-time sequencing information available to health care providers and public health officials — that’s a first,” concluded Jeffrey Kugelman, PhD, USAMRIID.