WHO declares a global health emergency over a rare Ebola strain with no vaccine

The World Health Organization's Director-General on 17 May determined that an outbreak of Ebola disease caused by Bundibugyo virus in the Democratic Republic of the Congo and Uganda constitutes a public health emergency of international concern (PHEIC) — the organization's highest level of alert — while stopping short of calling it a pandemic emergency under the International Health Regulations [s1].

The case count behind that determination was, by the standards of past Ebola PHEICs, still small. As of 16 May, WHO had recorded eight laboratory-confirmed cases, 246 suspected cases and 80 suspected deaths across at least three health zones in Ituri Province, DRC — Bunia, Rwampara and Mongbwalu — plus two laboratory-confirmed cases in Kampala, Uganda, including one death, in travelers from the DRC [s1]. A third suspected case, in a traveler who had gone from Ituri to Kinshasa, tested negative on confirmatory testing [s1].

An emergency declared ahead of the usual process

The determination came with a procedural twist. Under Article 12 of the IHR, the Director-General typically convenes an Emergency Committee of outside experts to advise on whether a PHEIC determination is warranted before making it. In this case, the WHO statement says the Director-General made the determination "after having consulted the States Parties where the event is known to be currently occurring" — the DRC and Uganda — and says a committee will be convened "as soon as possible" to advise on the temporary recommendations that follow, rather than beforehand [s1].

WHO's statement thanks both countries' governments for their "commitment to take necessary and vigorous actions to bring the event under control," and for their "frankness in assessing the risk posed by this event to other States Parties" [s1].

Why WHO judged this extraordinary

The IHR defines a PHEIC around three criteria, and WHO's determination statement addresses each one directly for this event.

On whether the event is extraordinary: the statement points to unusual clusters of community deaths with symptoms compatible with Bundibugyo virus disease across several health zones in Ituri, and to at least four deaths among healthcare workers in a clinical picture suggestive of viral hemorrhagic fever — raising concern about transmission inside health facilities and gaps in infection prevention [s1]. The statement also notes a high positivity rate in initial testing — eight positives among 13 samples collected across different areas — combined with rising trends in reported suspected cases, as evidence that "a potentially much larger outbreak" is underway than the confirmed count shows [s1]. Ongoing insecurity, a humanitarian crisis, high population mobility, the semi-urban nature of the outbreak's current hotspot, and a large network of informal health facilities all compound that risk, WHO says, "as was witnessed during the large Ebola virus disease epidemic in North Kivu and Ituri provinces in 2018-19" [s1].

On international spread: two confirmed cases had already reached Kampala by the time of the determination, both admitted to intensive care, and neighboring countries sharing land borders with the DRC are considered at high risk given population mobility and trade and travel links [s1].

On the need for coordinated international response: WHO says the event requires international cooperation to understand its true scale and to scale up surveillance, prevention and control measures across borders [s1].

The gap that makes Bundibugyo virus different

Bundibugyo virus is a distinct species within the Ebola family, and unlike the more familiar Ebola-Zaire strain that drove the 2014-16 West Africa epidemic and the 2018-20 DRC epidemic, there are currently no licensed vaccines or specific therapeutics against it [s1] [s2]. The case-fatality rate in the two previous known Bundibugyo virus outbreaks has ranged from 30% to 50% [s2]. Response is therefore limited to supportive care, contact tracing, isolation and the standard package of outbreak control measures — without the ring-vaccination tool that helped bring Ebola-Zaire outbreaks under control in recent years.

DRC's Ministry of Public Health, Hygiene and Social Welfare officially declared the country's 17th Ebola outbreak on 15 May, after INRB Kinshasa confirmed Bundibugyo virus disease in eight of 13 blood samples collected from Rwampara Health Zone [s2]. Uganda's Ministry of Health confirmed its own outbreak the same day, following the identification of an imported case — a Congolese man who died in Kampala [s2].

What WHO is asking countries to do

For the DRC and Uganda, WHO's advice calls for activating national disaster and emergency management mechanisms and establishing emergency operations centers under the authority of the head of state, to coordinate enhanced surveillance, contact tracing, infection prevention and control, risk communication, laboratory testing and case management across national and subnational levels [s1]. WHO says it is supporting response coordination, case management and cross-border preparedness, and has issued advice to other countries [s1].

What to watch

Whether the Emergency Committee, once convened, narrows or widens WHO's temporary recommendations — including on travel and trade measures, which the PHEIC determination itself does not specify beyond the general advice already issued. Whether the gap between confirmed and suspected cases closes as more samples are tested, which will indicate whether the 246 suspected cases reflect a true surge or a surveillance system still catching up. And whether the outbreak's urban and semi-urban footprint — unusual for an Ebola-family virus, which has more often spread in rural areas — changes the trajectory of transmission in the weeks ahead.

Sources

• [s1] World Health Organization, "Epidemic of Ebola Disease caused by Bundibugyo virus in the Democratic Republic of the Congo and Uganda determined a public health emergency of international concern," 17 May 2026. https://www.who.int/news/item/17-05-2026-epidemic-of-ebola-disease-in-the-democratic-republic-of-the-congo-and-uganda-determined-a-public-health-emergency-of-international-concern
• [s2] World Health Organization, "Ebola disease caused by Bundibugyo virus, Democratic Republic of the Congo & Uganda," Disease Outbreak News, 16 May 2026. https://www.who.int/emergencies/disease-outbreak-news/item/2026-DON602