FORT DETRICK, Md. — The Ebola virus appears to be even more insidious than scientists previously thought. Researchers from the U.S. Army Medical Research Institute of Infectious Diseases say, even after thorough medical treatment, Ebola can hide in the human brain and re-emerge long after the initial infection.
The new study involving monkeys with the virus found that Ebola can sit in the brain ventricular system before returning to cause another life-threatening infection. This area of the brain produces, circulates, and contains cerebrospinal fluid. Additionally, the team found that Ebola could safely hide in this brain region, even after monoclonal antibodies had cleared out the virus from every other organ.
Study authors say their new findings provide new insight into Ebola outbreaks in Africa, which scientists have linked to persistent infections in people who survived previous virus outbreaks. For example, the 2021 Ebola outbreak in Guinea originated in a persistently infected survivor of a larger outbreak five years earlier.
Until now, however, scientists have not been able to find the exact “hiding place” in former Ebola patients or understand why the virus suddenly returns long after treatment.
“Ours is the first study to reveal the hiding place of brain Ebola virus persistence and the pathology causing subsequent fatal recrudescent Ebola virus-related disease in the nonhuman primate model,” explains senior author Xiankun (Kevin) Zeng, Ph.D., in a media release. “We found that about 20 percent of monkeys that survived lethal Ebola virus exposure after treatment with monoclonal antibody therapeutics still had persistent Ebola virus infection—specifically in the brain ventricular system, in which cerebrospinal fluid is produced, circulated, and contained—even when Ebola virus was cleared from all other organs.”
Ebola has other hiding spots as well
During their study, researchers found two monkeys who initially recovered from an Ebola virus-related disease eventually suffered a fatal recurrence of Ebola virus infection. Study authors discovered severe inflammation and a “massive” Ebola virus infection in the brain ventricular system. However, there was no sign of infection in the other organs.
This isn’t the first study to document a fatal relapse of Ebola long after a patient recovered from an infection. A British nurse had a relapse of Ebola in the brain, developing a case of meningoencephalitis (a neurological condition causing brain inflammation) nine months after receiving treatment for a severe case of Ebola virus. Another vaccinated patient died six months after receiving monoclonal antibody therapeutics, during the 2018-2020 outbreak in the Democratic Republic of the Congo. That patient’s case also led to more human-to-human transmissions of the virus before their death.
Prior research has found that Ebola could hide in other regions of the body, like the vitreous chamber of eyes and the seminiferous tubules of testes. The new study is the first to reveal a specific area of the brain as an Ebola hiding spot.
“The persistent Ebola virus may reactivate and cause disease relapse in survivors, potentially causing a new outbreak,” adds USAMRIID’s Jun Liu, Ph.D., co-first author of the paper.
What exactly is Ebola?
The Ebola virus is one of the deadliest diseases on Earth to humans. It remains a major threat to the people of Africa, with three significant outbreaks taking place in 2021 alone.
The virus causes severe bleeding, organ failure, and can be fatal without serious medical care. Contact with bodily fluids, like blood, can spread Ebola between people rapidly. The initial symptoms of an Ebola infection include fever, headache, muscle pain, and chills. Later on, patients may suffer from internal bleeding which causes them to cough up or vomit blood.
“Fortunately, with these approved vaccines and monoclonal antibody therapeutics, we are in a much better position to contain outbreaks,” Zeng concludes. “However, our study reinforces the need for long-term follow-up of Ebola virus disease survivors—even including survivors treated by therapeutic antibodies—in order to prevent recrudescence. This will serve to reduce the risk of disease re-emergence, while also helping to prevent further stigmatization of patients.”
The study is published in the journal Science Translational Medicine.