Can Ebola be transmitted through semen? Can a man infect a woman through sex before symptoms appear or after he has recovered?
Dr Samoel Khamadi, an infectious disease scientist at the Kenya Medical Research Institute (Kemri), says blood remains the standard specimen used by doctors to diagnose people suspected of having the Ebola virus.
“However, semen testing becomes relevant in specific circumstances; particularly when doctors are investigating whether the virus has persisted after recovery, or when they are trying to explain a transmission that cannot be accounted for in any other way,” explains Dr Khamadi.
Ebola virus has been found in the semen of male survivors for up to 16 to 18 months after the onset of symptoms, according to past studies. A Sierra Leone study revealed that some male Ebola survivors still had traces of the Ebola virus in their semen 16 to 18 months after being discharged from hospital, although this became much less common over time. So doctors, being cautious, usually recommend that men who recover from Ebola use condoms or abstain from sex, including oral sex.
Why semen, and why does the virus linger after recovery?
Dr Khamadi says Ebola can remain in the testes even after it has cleared from the blood because the testes have a limited immune response, meaning the body may not clear the virus there as quickly as it does in other parts of the body.
“Ebola virus does not necessarily disappear from every part of the body at the same time. In male survivors, Ebola may remain in the semen after it has cleared from the blood, and can be transmitted through sexual contact,” he says.
Dr Khamadi cites past studies during the 2014–2016 West African Ebola outbreak, when researchers examined Ebola cases where there was no clear history of contact with someone who was actively ill.
“They were trying to find out how these women got Ebola because they had not been in contact with someone who was actively ill with Ebola,” he says.
“When they tested him, the blood was negative [for the Ebola virus], but when they tested the semen, it was positive,” he says.
Ebola virus has been found in the semen of male survivors for up to 16 to 18 months after the onset of symptoms.
Photo credit: Shutterstock
How semen testing is done
A male survivor produces a semen sample, which is collected and sent to a laboratory for testing. Dr Khamadi says the sample is obtained through stimulation. Testing is repeated because one negative result does not necessarily mean that Ebola is no longer detectable in the semen.
Dr Patrick Amoth, Director General for Health, said in a past interview that survivors undergoing follow-up have their semen tested “every month until two consecutive negative results are obtained.”
“However, after 12 months with no symptoms, the patient will continue to be monitored, and we will advise them to use barrier contraceptive methods such as condoms. Then they can be reintegrated into the community,” explained Dr Amoth.
This 12-month period does not mean that Ebola always disappears from the semen of survivors after exactly one year, as viral RNA has been detected for longer in some cases. RNA is genetic material from the virus. However, detecting it does not prove that the virus is still alive, so a positive semen test does not automatically mean that the sample is infectious.
Is similar testing necessary for women?
According to experts, women who recover from Ebola do not require routine testing of vaginal fluids.
Dr Khamadi says that blood remains the normal specimen for diagnosing or monitoring Ebola infection.
“You don’t normally test vaginal fluid,” he says.
The World Health Organisation (WHO) reports show that some studies have detected Ebola RNA in vaginal fluid but not isolated the infectious virus from it. Therefore, routine vaginal-fluid testing is not currently recommended.
Women who recover from Ebola may require follow-up care in certain circumstances. The WHO says that Ebola can persist in pregnancy-related tissues and fluids in women who were infected while pregnant, as well as in breast milk in women who were infected while breastfeeding.
But how does Ebola reach people in the first place?
Ebola can be transmitted from animals to humans, with fruit bats believed to be the natural hosts of orthoebolaviruses (a group of highly dangerous viruses that cause Ebola disease).
Once a person is infected with Ebola, transmission mainly occurs through direct exposure to infectious body fluids or materials contaminated by those fluids.
The risk is different when coming into contact with someone who has recovered from Ebola compared with someone who is actively sick.
People who may have been exposed should consider not just how close they were to the patient, but whether they came into contact with infectious body fluids or contaminated materials.
Blood is the standard specimen used by doctors to diagnose Ebola but the virus has been found in the semen of male survivors.
Ebola disease typically presents with symptoms such as fever, fatigue, muscle pain, headache and sore throat. As the illness progresses, vomiting, diarrhoea, rash and, in some cases, bleeding may develop.
Blood is the main specimen used for laboratory confirmation, as the virus circulates in the blood during active illness.
Dr Amoth says that the incubation period (the time between infection and the appearance of symptoms) is between two and 21 days. This means that anyone identified as a contact will have to remain in isolation for up to 21 days.
“After that, we will be able to perform a test to confirm that they are negative. Those who test negative will then be released. Anyone in isolation who develops symptoms will be classified as a case and transferred to an Ebola treatment unit for care,” he says.
What counts as contact with Ebola?
Dr Khamadi says that the Ebola virus is not airborne and does not spread simply because two people breathe the same air.
“There is no distance rule. What matters is exposure to infectious body fluids,” says Dr Khamadi.
“Someone standing several metres away without touching the patient or fluids is not exposed in the same way as a healthcare worker or relative washing a patient, handling vomit, or cleaning contaminated bedding without protective equipment,” he explains.
The risk increases when the patient is vomiting, has diarrhoea, is bleeding, or is producing fluids that can contaminate the environment.
“You cannot have somebody with Ebola in the same room as other people,” he says. “You should avoid any form of physical contact with an active Ebola patient.”
What about handshakes? He clarifies that a handshake does not automatically transmit Ebola. However, if an infectious fluid from a patient’s hand comes into contact with another person's broken skin, eyes, nose or mouth, the virus could enter the body.
Kissing an actively infected person should also be avoided because it involves saliva and close contact.
The same principle applies to clothing and bedding: the risk comes from being contaminated by infectious fluids. Dr Khamadi advises against sharing personal items like bed sheets and towels.
So what changes after recovery or death?
A recovered Ebola survivor is not automatically infectious through ordinary social contact. Experts do not recommend isolating recovered patients simply because they previously had Ebola. Survivors receive follow-up care and counselling, and where available, targeted testing for sites where Ebola may persist.
Meanwhile, after death, the Ebola virus can remain transmissible in the body. Traditional funeral practices involving washing, touching or preparing the body can expose people to infectious material.
