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A new preliminary genetic analysis suggests that the current Ebola outbreak in Guinea may have originated with a survivor of the 2014-2016 West African Ebola outbreak, rather than from an animal-to-human transmission.
According to the pre-print report, the outbreak likely started with the survivor infecting a sexual partner with the deadly virus through semen — after the virus lay dormant in the man for at least 5 years.
The analysis, posted online Friday, was conducted by scientists from Guinea, the Institut Pasteur in Senegal, the University of Nebraska Medical Center, the University of Edinburgh, and the company PraesensBio.
According to the Infectious Diseases Society of America (IDSA), the longest an Ebola survivor was believed to have shed the virus was about 500 days.
The previous Ebola outbreak resulted in 28,000 cases and 11,000 deaths mainly in Guinea, Liberia, and Sierra Leone, according to the new report. So far, the current outbreak in Guinea has resulted in 18 cases and has killed nine people, according to The New York Times.
The news is “sobering,” said William Schaffner, MD, a communicable disease epidemiologist and pandemic preparedness expert at Vanderbilt University in Nashville, Tennessee, in an interview with Medscape Medical News.
“Who would have thought that the Ebola virus could remain latent in a person — a male — for five years and then set off another outbreak?” Schaffner said. “Until this news came in, I think we all thought this latest Ebola outbreak was a consequence of an introduction from an animal species, probably a fruit bat, into the human population.”
“This gives a whole new public health resonance to the notion that male Ebola survivors are a potential reservoir of this infection for many years,” he added.
Schaffner explained that the testes, in addition to the eye and the central nervous system, are among the three immunologically protected locations in the body where the Ebola virus has hidden.
The new report begs the question, he said, about whether some of the past outbreaks in Africa weren’t introduced from the wild but instead occurred because a survivor initiated the infection in a new partner.
The particular danger of the virus lying dormant in the testes, rather than the eye or in the CNS, is that it could be transmitted to someone sexually, Schaffner noted.
The findings in the genetic analysis could exacerbate the stigma for survivors, he said.
It also raises the question about whether widespread vaccinations are needed in equatorial Africa. Additionally, even though Ebola vaccines are very effective, he said, it isn’t known how long they could protect people.
“It would be monstrously difficult to do,” Schaffner said. “You’d be vaccinating millions of people.” Another public health measure may be promoting more condom use, he noted, which comes with its own set of difficulties.
In light of this latest news, male survivors will move into the research spotlight, he said, and volunteers will be asked to provide semen specimens to find out whether this is a one-time event or something that happens commonly.
The location of the immunologically protected areas in the body also make it difficult to study, beyond asking for semen samples, Schaffner said.
The information in the report is convincing, he said, because it determined that when the virus in the current carrier and the virus in West Africa 5 years ago were compared, the viruses were almost identical.
“That provided conclusive evidence from the laboratory that this could not have been a virus that was introduced from the wild,” Schaffner said, “because by this time, viruses in the wild have accumulated many, many other mutations.”
Angela Rasmussen, MD, a virologist at Georgetown University’s Center for Global Health Science and Security in Washington, DC, noted on Twitter that, “[W]e’d expect viruses that have been replicating for 5-7 years, even at low levels, to have many more mutations. Like hundreds. These have 12.”
Michael Ryan, MD, World Health Organization (WHO) emergencies chief, said in a briefing on Friday that the WHO has sent more than 30,000 vaccine doses to the country.
Schaffner has disclosed no relevant financial relationships.
Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News and Nurse.com and was an editor at the Chicago Sun-Times, the Cincinnati Enquirer, and the St. Cloud (Minnesota) Times. Follow her on Twitter at @mfrellick
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