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.

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.

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 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.

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.

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Mogomotsi Magome in Johannesburg, Jamey Keaten in Geneva, and Jonathan Poet in Philadelphia, contributed to this report.

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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.