The virus causing an outbreak in Congo suspected of killing more than 200 people is less common than others that cause Ebola disease, which is complicating the response, because there are no specific treatments or vaccines.
“There’s nothing even close to ready for clinical trials,” said Dr. Celine Gounder, an infectious disease specialist and epidemiologist who treated patients in West Africa during the 2014-2016 Ebola epidemic. “And so that means responders, healthcare workers and other aid workers are really back to the basics.”
Last week, the World Health Organization said that its advisory groups had identified some potential vaccines and therapies to test, but recommended they be used exclusively in clinical trials to ensure they are safe and effective. Each would require months of development.
Here’s what to know about Bundibugyo virus, the rare species behind the outbreak, and the vaccines and treatments being studied to help fight it.
Previous instances of the virus
Bundibugyo virus has caused two other outbreaks, all in the same region of the Congo River basin, said Dr. Tom Ksiazek, a University of Texas Medical Branch virologist and veterinarian. He directed the U.S. Centers for Disease Control and Prevention’s Special Pathogens Branch, which first identified the virus in 2007.
Other viruses that cause Ebola disease are the Ebola virus (sometimes called the Zaire virus), the Sudan virus, and the Taï Forest virus, which isn’t known to cause large outbreaks.
How it’s spread
The virus is circulated through close contact with sick or deceased patients’ bodily fluids, such as sweat, blood, feces or vomit. Healthcare workers and family members caring for sick patients face the highest risk, experts said.
“So very often we see doctors and nurses among the first to be infected and to die,” said Gounder, editor-at-large for public health at KFF Health News.
Less lethal, but still extremely dangerous
From the few outbreaks health experts have seen, Bundibugyo might be slightly less deadly than Ebola virus or Sudan virus.
“I think a 30%-plus mortality rate is still quite scary, but it’s hard to say with a lot of precision because we don’t have a lot of experience,” Gounder said.
How to care for patients
In the other two Bundibugyo outbreaks, initial cases were identified early, Ksiazek said, allowing for a quick public health response: getting healthcare workers proper protective equipment, finding and isolating people who were exposed and offering supportive medical care to patients. Proper medical care “reduces mortality significantly,” he said.
That includes giving patients lots of IV or oral fluids, Gounder said.
Vaccine candidates emerge, but more testing needed
There are three promising vaccine candidates, according to global health officials. They are:
— A vaccine similar to Merck’s Ervebo vaccine, which targets the Ebola virus – not the Bundibugyo virus causing the current outbreak. A Bundibugyo-specific version using the same vaccine platform is being developed by the International AIDS Vaccine Initiative. It would likely need at least seven months, before it could be tested in a clinical trial, WHO has said.
— A vaccine built on the same platform as the Oxford University/AstraZeneca COVID-19 vaccine. India’s Serum Institute is making doses, which could become available within two to three months for a clinical trial, but WHO officials say more animal testing is needed to ensure it can be used against the Bundibugyo virus.
— A vaccine being developed by Moderna, using the same mRNA technology as its COVID-19 vaccines. The company says it’s building off earlier research and development of related Ebola vaccines and could move immediately to broader clinical testing if early safety tests are successful.
WHO’s list of priority treatments
The U.N. health agency’s independent experts recommended prioritizing three therapies for clinical trials: Antibody therapies from Mapp Biopharmaceutical and Regeneron, plus Gilead Sciences’ antiviral drug remdesivir.
Mapp’s experimental antibody treatment, MBP134, targets several forms of Ebola, including Bundibugyo. Regeneron’s treatment, maftivimab, is a component of Inmazeb, which was approved by U.S. regulators in 2020 for the Ebola virus.
Remdesivir, sold under the brand name Veklury, was approved in 2020 as a COVID-19 treatment.
WHO also said an experimental antiviral drug called obeldesivir should be studied for protecting people exposed to Ebola victims. The Gilead drug, which is still in mid-stage clinical trials, should be evaluated to see if it prevents close contacts from developing Ebola disease, the agency said.
How public health workers are trying to contain the outbreak
Health workers are now working to find and isolate cases, trace their contacts and educate people about how to avoid the virus. In the West African Ebola epidemic, ensuring safe methods of burial was key to stopping the spread, said Gounder, because people were getting sick from preparing their loved ones’ bodies for funeral rites. Making sure health workers have proper protective equipment is also critical, experts said.
“Of course, it’s problematic because vaccines are some of our best tools for combating infectious diseases,” said Lina Moses, an epidemiologist and disease ecologist at Tulane University. But other public health tools — public education, contact tracing, quick testing — still work, she said.
“It’s important to keep in mind that every single Ebola outbreak that has occurred in the (Democratic Republic of the Congo) — we’re on our 17th now — has been stopped,” she said.
___
Mogomotsi Magome in Johannesburg, Jamey Keaten in Geneva, and Jonathan Poet in Philadelphia, contributed to this report.
___
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.
Copyright © 2026 The Associated Press. All rights reserved. This material may not be published, broadcast, written or redistributed.
