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| An electron micrograph scan shows the Ebola virus emerging from an infected cell. |
"These results come at a critically important time, reminding us that while Ebola case numbers continue to plummet, Ebola survivors and their families continue to struggle with the effects of the disease," Bruce Aylward, the World Health Organization's top Ebola official, said in a statement. "[The study] provides further evidence that survivors need continued, substantial support for the next 6 to 12 months to meet these challenges and to ensure their partners are not exposed."
The findings, published in the New England Journal of Medicine, are part of a long-term effort to decipher the mysteries that still surround the deadly disease. While the unprecedented Ebola outbreak in West Africa has killed more than 11,000 people, it also has left behind something previous outbreaks did not -- thousands of survivors that researchers hope can teach us more about the virus.
The study involved analyzing semen samples from 93 Sierra Leonean men who had survived Ebola.
Researchers detected the presence of the virus's genetic material in the semen of all nine men tested in the first three months after their illness began. More than half of the 40 men tested between four and six months after the onset of their symptoms also tested positive, as did a quarter of the 43 men tested between seven to nine months after their illness began.
The findings shed new light on how long the virus can remain in the body. As recently as last October, the WHO noted that while the virus is spread primarily through contact with blood, feces and vomit -- and typically during the height of illness -- it also had been detected in breast milk, urine and semen. "In a convalescent male, the virus can persist in semen for at least 70 days; one study suggests persistence for more than 90 days," the organization wrote then. The study suggests that the virus can hang around even longer than many researchers expected.
But plenty of questions remain. The authors acknowledged that they still lack data about how the presence of Ebola virus RNA in semen relates to the likelihood of actual transmission. Despite some suspected instances of Ebola being spread through sexual activity, it is exceedingly rare, and "the risk of sexual transmission is unknown and is being investigated," the study states.
The explanation for why some men retain fragments of the Ebola virus in their semen for months while others clear the virus also remains unclear. Researchers at the Centers for Disease Control and Prevention are conducting more tests on the samples to determine whether the virus is live and potentially infectious. In the meantime, health officials have urged the more than 8,000 male Ebola survivors to abstain from sex or use condoms until no remnants of the virus remain in their semen.
The study, conducted jointly by the CDC, the WHO and the Sierra Leone Ministry of Health, comes as the countries hard-hit by the Ebola crisis are pushing to end the outbreak nearly two years after it began. The epidemic is now confined to small areas of Guinea and Sierra Leone, the WHO said. Liberia remains free of Ebola. In general, the epidemic is considered over in a country when no new cases are identified for 42 days, twice the incubation period of the virus.
However, it is believed that, so long as there is a case of Ebola in any part of the world, there is the risk that it could be imported into any other part of the world.