Guinea study finds Ebola RNA in semen up to 9 months after infection

A study of Ebola virus disease survivors in Guinea has added to previous evidence that the virus can persist for as long as 9 months in the semen of survivors, reinforcing the concern about a risk of sexual transmission for months after recovery.

An international team of researchers tested 98 semen samples from 68 Ebola survivors in Conakry and Macenta, Guinea, from March through October 2015, according to their May 3 report in the Journal of Infectious Diseases. Polymerase chain reaction (PCR) results for Ebola RNA were positive for 10 samples collected from eight men up to 276 days (9 months) after their first symptoms.

The proportion of specimens that tested positive decreased over time, with positive results for 28.6% of specimens (4 of 14) obtained between 1 and 3 months after disease onset, 16.7% (3 of 18) collected at 4 to 6 months, and 6.5% (2 of 31) obtained at 7 to 9 months, the report says.

The researchers did not determine whether the samples contained infectious virus. "Semen probably does not remain infectious during the whole period, and viral isolation and sequencing will soon be performed . . . to determine the infectivity of samples," they wrote.

In a study published in October 2015, Ebola RNA was found in the semen of 11 of 43 Ebola survivors who were tested between 7 and 9 months after their illness. And reports published in 2015 suggested that an Ebola case in a Liberian woman was probably caused by sexual transmission from her husband, an Ebola survivor.

The World Health Organization (WHO) has recommended that Ebola survivors abstain from sex or use condoms for up to 6 months after Ebola infection if semen testing is unavailable.

May 3 J Infect Dis report

Accompanying May 3 J Infect Dis commentary

Related CIDRAP News reports: Apr 5, 2016, and Oct 14, 2015

Post-epidemic Ebola cases in Liberia ascribed to lingering silent infection

A small Ebola outbreak that occurred in Liberia several months after its epidemic was declared halted was due to some unknown, persistently infected source, rather than an environmental source or cases in a neighboring country, according to findings from a large international team of scientists.

Active Ebola transmission in Liberia was stopped in February 2015, notes the report, published Apr 29 in Science Advances. Subsequently, one case was confirmed in March 2015, and a cluster of seven cases popped up in June of the same year.

The authors used epidemiologic and genomic data to investigate the source of that second post-epidemic flare-up, which occurred in Needowein, Margibi County. They said they found links between the Needowein cluster and a cluster of cases that had occurred nearly a year earlier in the nearby Barclay Farm community.

The researchers couldn't pinpoint the source, however. They found that Ebola virus genomes from two Barclay Farm patients differed from Ebola genomes from the Needowein outbreak by only one nucleotide, suggesting direct transmission, but the Barclay Farm patients had died in August 2014.

Another possible link was a woman from Barclay Farm who had a presumed Ebola infection and who moved to Needowein, but her case was never confirmed, the report says. The authors speculate that the source of the virus might have been an unidentified Ebola survivor with ties to the Barclay Farm cluster.

The report notes that Liberia was again declared free of Ebola in September 2015, but three more linked cases were confirmed in November. And just over a month ago, on Apr 1, the WHO reported yet another new case in Liberia. The WHO warned in March that sporadic cases are likely to occur because of lingering infections in survivors.

Previous reports have shown that the virus can linger in immune-protected parts of the body, such as the eyes and testes, and sexual transmission has been suspected as the source of some recent illness clusters (see item above).

Apr 29 Science Advances report

Apr 1 CIDRAP News story on most recent Ebola case in Liberia