Study reveals risk factors for Ebola persistence in semen
Older age and lower illness severity are associated with a higher risk for persistent Ebola virus in semen, according to a study published in Clinical Infectious Diseases.
“During and following the 2014 Ebola virus disease outbreak in West Africa, we saw that some male survivors ... could have persistent Ebola virus in their semen up to a year or more following their recovery from acute illness,” Aaron Kofman, MD, a medical officer in the CDC’s Division of Healthcare Quality Promotion, told Healio.
According to the study, most men clear Ebola virus from their semen within a year, but Kofman noted that in February 2016, a flare-up of Ebola in Guinea and Liberia occurred following sexual transmission of the virus from a male survivor 531 days after his acute illness.
Additional studies have reported persistence in the semen of survivors for more than 2 years after disease onset, including one case where it persisted for 40 months, according to Korman and colleagues.
“Our study was prompted by the question of what risk factors, if any, contribute to the lengthy persistence of Ebola virus in the semen of some male survivors of Ebola virus disease,” Kofman said. “Identification of such risk factors are important to the prevention of future sexual transmission events, as they may enable better identification of male survivors who are at highest risk of prolonged Ebola virus persistence.”
Koffman said understanding these risk factors may also provide useful clues to help experts better understand the pathophysiology of Ebola virus in the testes and other immunologically protected sites in the body.
Kofman and colleagues enrolled 131 male Ebola survivors from Liberia. Kofman explained that the team compared “early clearers,” or those who had cleared virus from their semen within 1 year of discharge from the Ebola treatment unit, with “late clearers,” or people who still had detectable Ebola virus RNA in their semen more than a year after discharge.
The study revealed that compared with early clearers, late clearers were older (median age 42.5 years; P = .0001) and had fewer severe clinical symptoms at the time of their acute illness (median of two symptoms; P = .006). Compared with early clearers, late clearers also had more lens opacifications (OR = 3.9; 95% CI, 1.1-13.3) and, after adjusting for age, higher total serum IgG3 titers (P = .007) and increased expression of the HLA-C*03:04 allele (OR = 0.14; 95% CI, 0.02-0.7).
Kofman said the risk factors identified in the study may enable longer term monitoring for a select group of “higher risk” survivors who have one or more of the risk factors. For example, he explained that an Ebola survivor semen testing program may be able to prioritize the ongoing testing of a survivor who is 52 years old with lens opacifications, and provide him with counseling about safe sexual practices until the virus has been cleared from his semen.
“We hope that future corroboration of these findings may lend additional insights into the nature of host determinants in the persistence of Ebola virus in immunologically protected sites of Ebola survivors,” Kofman said.