The World Health Organization declared a public health emergency of international concern on Sunday over an Ebola outbreak in eastern Congo and neighboring Uganda. More than 336 suspected cases and 88 deaths have been reported, and a confirmed case has now been detected in Kinshasa — about 1,000 kilometers from the epicenter — raising fears of wider spread.

Here is what to know.

What is happening and where?

The outbreak began in April in Mongwalu, a high-traffic mining area in Congo's Ituri province in the east of the country. By the time health authorities were alerted via social media on May 5, 50 people had already died. The earliest known case, a 59-year-old man, developed symptoms on April 24 and died three days later.

Cases have since spread to two other health zones in Ituri, including Bunia, the provincial capital near the Ugandan border. Two cases have been confirmed in Uganda — both in people who had traveled from Congo, one of whom died in Kampala. A laboratory-confirmed case has also been reported in Kinshasa, suggesting the virus may be spreading beyond the original outbreak zone.

What makes this outbreak different?

This outbreak is caused by the Bundibugyo virus — a rare variant of Ebola for which there are no approved vaccines or treatments. Although Congo has experienced more than 17 Ebola outbreaks since 1976, this is only the third time the Bundibugyo strain has been detected anywhere in the world.

The previous two Bundibugyo outbreaks occurred in Uganda in 2007–2008, infecting 149 people and killing 37, and in Congo in 2012, with 57 cases and 29 deaths. The strain appears to have a lower fatality rate than the Ebola Zaire virus responsible for most of Congo's past outbreaks, but the absence of any approved treatment or vaccine makes it significantly harder to manage.

How does Ebola spread?

Ebola is not airborne. It spreads through direct contact with the bodily fluids — blood, vomit, feces, or semen — of an infected person, or with surfaces contaminated by those fluids. Fruit bats are believed to be the natural reservoir of the viruses that cause Ebola; people can be infected through contact with bats or other infected animals, and then spread it person to person.

Symptoms typically appear two days to three weeks after exposure, usually within a week. They begin with flu-like signs — fever, fatigue, aches, sore throat — before progressing to vomiting, diarrhea, rashes, and in some cases internal and external bleeding. The average fatality rate across all Ebola outbreaks is around 50%, though it has ranged from 25% to 90%.

Why is containment difficult?

Several factors are complicating the response.

Ituri is remote, with poor road networks and more than 1,000 kilometers between the outbreak zone and Kinshasa. Armed militant groups have killed dozens and displaced thousands in parts of Ituri over the past year, severely disrupting health services and population movement. Mining activity has driven significant cross-border movement between Congo and Uganda, making contact tracing difficult.

Africa CDC Director-General Dr. Jean Kaseya said a high number of active cases remain undetected in the community and that "significant uncertainties" remain about the true scale of the outbreak. Four healthcare workers have died showing Ebola symptoms. The WHO said the spread to Kampala, the high proportion of positive tests among samples taken, and clusters of deaths across Ituri all suggest the outbreak may be larger than current figures indicate.

What is the WHO emergency declaration?

The WHO's declaration of a public health emergency of international concern — the same designation used for COVID-19 and mpox — is designed to trigger a coordinated international response and unlock donor funding. It does not mean the outbreak meets the criteria for a pandemic, and the WHO has advised against closing international borders.

The declaration has a mixed track record. When the WHO issued a similar alert over mpox in Africa in 2024, experts said it did little to accelerate the delivery of diagnostics, medicines, or vaccines to affected countries. The WHO has released $500,000 so far to support the response; Africa CDC has mobilized $2 million, which it acknowledged is "a small fraction" of what is urgently needed.

Is there a vaccine or treatment?

No. There are approved vaccines and therapeutics for the Ebola virus — the strain responsible for most of Congo's past outbreaks — but none for the Bundibugyo strain. Four therapeutics are under consideration but none is approved. No vaccine is currently in active development for Bundibugyo, in part because pharmaceutical companies have historically shown limited interest in developing vaccines for rare strains with lower death tolls.

Africa CDC's director has called on the continent to build its own vaccine manufacturing capacity, warning that reliance on external suppliers has repeatedly left Africa behind during outbreaks. "If we are serious on this continent, we need to manufacture what we need," Kaseya said.

How does this compare to past outbreaks?

The worst Ebola outbreak on record was the 2013–2016 epidemic in West Africa, primarily in Guinea, Liberia, and Sierra Leone, which caused more than 28,000 cases and 11,000 deaths. A small number of cases were recorded in the US, UK, Italy, and Spain.

The second-largest occurred in Congo's North Kivu, South Kivu, and Ituri provinces between 2018 and 2020, with more than 3,400 cases and 2,200 deaths. That outbreak, like the current one, involved Ituri province and spread into Uganda.

Ebola was first identified in 1976 during two near-simultaneous outbreaks in what is now South Sudan and Congo. The disease was named after the Ebola River, near where the Congo outbreak occurred.