In the latest study, 26% of the male survivors had sperm that tested positive for EVD genetic material.
The study is published in the New England Journal of Medicine and shows preliminary results of a long-term study conducted by the Sierra Leone Ministry of Health and Sanitation, the World Health Organization (WHO) and the US Centers for Disease Control and Prevention (CDC).
According to the researchers, the number of new cases of Ebola virus disease (EVD) has declined in Western Africa from a high of 1,063 cases during the week of October 9, 2014, to fewer than 10 cases each week for 11 straight weeks as of October 7, 2015.
They note that, though rare, suspected cases of sexual transmission of EVD have been reported, which is why they are further investigating the topic.
In 1967, there was a confirmed case of sexual transmission of the related Marburg filovirus from a male survivor to a female partner, supporting the view that Ebola can be passed through semen.
The main source of transmission of Ebola is through direct contact with the body or bodily fluids of a person with the virus - or from the body of a person who died from it. The researchers note, however, that EVD can persist in the bodily fluids of survivors during recovery, which could result in transmission.
'Further evidence survivors need continued support'
As part of the study, a total of 93 men aged 18 or over in Freetown, Sierra Leone, submitted semen samples that were tested for the presence of EVD genetic material. These men enrolled in the study between 2-10 months after their symptoms began.
- The average EVD fatality rate is around 50%
- First outbreaks occurred in remote villages in Central Africa
- The recent 2014 outbreak in West Africa involved major urban and rural areas, with cases traveling to other parts of the world.
Of the men who were tested during the first 3 months of their illness, 100% tested positive for presence of EVD in their semen; of the men who were tested between 4-6 months after symptoms began, 65% tested positive.
Results also showed that 26% of the men tested between 7-9 months after their illness began had semen that tested positive for EVD.
The researchers say it is unclear as to why some study participants had cleared remnants of the virus from semen earlier than others, but the CDC are carrying out further tests of the samples to establish whether the virus is live and possibly infectious.
"These results come at a critically important time," says WHO's Bruce Aylward, "reminding us that while Ebola case numbers continue to plummet, Ebola survivors and their families continue to struggle with the effects of the disease."
"This study provides further evidence that survivors need continued, substantial support for the next 6-12 months to meet these challenges and to ensure their partners are not exposed to potential virus."
CDC Director Dr. Tom Frieden adds that survivors of the disease "face an increasing number of recognized health complications. This study provides important new information about the persistence of Ebola virus in semen and helps us make recommendations to survivors and their loved ones to help them stay healthy."
Safe sex and Ebola
The researchers note that until more is known, the thousands of male Ebola survivors need education, counseling and regular testing so they know if the virus remains in their semen.
During this time, WHO have issued some recommendations, including:
- Ebola survivors should be issued with condoms
- Survivors and their sexual partners should either abstain from all types of sex or observe safe sex until their semen has tested negative two times
- Until their semen has twice tested negative, survivors and partners should immediately wash their hands with soap and water after any physical contact with semen - including after masturbation.
The recommendations also advise that "all survivors, their partners and families should be shown respect, dignity and compassion."
Yusuf Kabba, national president of the Sierra Leone Association of Ebola Survivors, says that the "EVD survivors who volunteered for this study are doing something good for themselves and their families and are continuing to contribute to the fight against Ebola and our knowledge about this disease."
In August of this year, Medical News Today reported on the first ever successful field testing of an Ebola vaccine.