The Ebola virus
The Ebola virusNIAID: The National Institute of Allergy and Infectious Diseases

Researchers at Boston University say they have detected signs that the deadly Ebola virus causes an immune response in monkeys four days before they begin exhibiting symptoms.

More research is needed, but the discovery raises the prospect of diagnosing the disease earlier in humans, allowing earlier treatment to help patients and earlier quarantine to control breakouts, the university said in a statement Wednesday.

“Right now, we wait for diagnosis until the virus spills out of primary infection sites into the blood,” says Emily Speranza, who recently received her doctorate from Boston University’s bioinformatics program and is one of the first authors on the paper. “At that point, it’s already tremendously far along.”


“If you can start treating someone very, very early on after exposure, they’re less likely to develop really severe disease,” Speranza said in the statement. “And if you can identify people who are sick before they even show symptoms, you can better quarantine and actually control outbreaks.”

The research was led by John Connor, a professor at Boston University School of Medicine and a researcher at the university’s National Emerging Infectious Diseases Laboratories, a biolab built on the BU medical campus in the South End.

The US Army Medical Research Institute of Infectious Diseases, or USAMRIID, collaborated with the BU researchers. The study was published Wednesday in the journal Science Translational Medicine, the university said.

Speranza looked at a massive trove of data collected from a group of monkeys that had been infected with Ebola at the USAMRIID biolab at Fort Detrick in Maryland.

John Connor and Emily Speranza
John Connor and Emily SperanzaMark Fleming/Cydney Scott

Speranza’s analysis found a handful of the monkeys’ genes kicking into gear as part of the innate immune response, the body’s first defense against disease, the university said. The reaction happened four days before symptoms.

She also looked at data from blood samples collected from people during the 2014-2016 outbreak in Guinea.


Connor said in a telephone interview that the human data showed genetic changes similar to what happened in the monkeys, but the data did not go back before the patients had symptoms.

Connor said more research is needed into whether in humans, as in the monkeys, the changes begin four days before symptoms appear.

“That’s our hypothesis going forward, that it would be an excellent thing to investigate,” he said.

Connor noted that other scientists have found similar early immune responses in monkeys exposed to Lassa fever and humans exposed to the flu.

Still more research would be needed to sort out the specific markers of the human response to Ebola — and then create some kind of easily administered test, he said.

Such a test could be a boon to people who have been exposed to Ebola, including doctors treating Ebola patients. Even if a test could only indicate the onset of a viral infection, it could be a good thing to have, he said.

Until now, the only option for treating those who have been in contact with the terrible disease but aren’t sick yet has been: “Let’s just watch them and see if they spike a fever,” he said. By then, for many, it’s already too late.

Andrew Pekosz, a professor of molecular microbiology and immunology at Johns Hopkins University, said in an e-mail that the BU researchers’ study was interesting, contained some surprising findings, and could prove valuable.


“As the authors state at the end, these kinds of studies can set up key “signals” to look for after infection which could be used to determine when or even if a person will come down with severe disease. Being able to differentiate between ‘you’ve been exposed to the virus’ and ‘you are about to become very sick from your exposure to the virus’ has important implications for patient care and for intervention therapy,” he said.

Dr. Daniel Lucey, an adjunct professor of microbiology and immunology at Georgetown University Medical Center and a senior scholar with the O’Neill Institute for National and Global Health Law, also saw promise in the BU research.

“If some future test that was unique for Ebola virus infection could diagnose Ebola before fever began, then it could be very helpful in two ways: (1) to the patient, in terms of earlier treatment and (2) to Public Health, in terms of preventing spread of Ebola virus, because spread to other people through contact with infected body fluids occurs only after fever begins,” he said in an e-mail.