The World Health Organization (WHO) has declared the latest Ebola outbreak in the Democratic Republic of the Congo (DRC) and neighbouring Uganda a “public health emergency of international concern” after the virus killed nearly 90 people.

The outbreak, originating in eastern DRC’s Ituri province, involves the rare Bundibugyo strain of Ebola. The variant has no approved vaccine or treatment.

Health authorities said the outbreak poses a high regional risk because infections have already been detected in Uganda and cases linked to the outbreak have reached Congo’s capital, Kinshasa.

The WHO, however, stopped short of declaring a pandemic, saying it did not meet the necessary criteria. The United Nations agency advised countries against closing borders or restricting trade.

Here is what we know:

What do we know about the outbreak?

The outbreak was first reported in Ituri province in the northeastern DRC on Friday near the borders with Uganda and South Sudan, according to Africa’s Centres for Disease Control and Prevention (Africa CDC). As of Saturday, the centre had reported 88 deaths and 336 suspected cases.

The outbreak began in Mongwalu, a busy mining area. Infected people later travelled out of the area, sought treatment in other places and spread the disease. Africa CDC warned that population movements, weak healthcare infrastructure and violence by armed groups in Ituri could complicate containment efforts.

The outbreak’s patient zero was a nurse who arrived at a health facility in Ituri’s capital, Bunia, on April 24, showing Ebola-like symptoms, DRC Health Minister Samuel-Roger Kamba said.

Meanwhile, Uganda has recorded two laboratory-confirmed cases linked to travellers arriving from the DRC, including one death in the capital, Kampala.

“The number of cases and deaths we are seeing in such a short timeframe, combined with the spread across several health zones and now across the border, is extremely concerning,” warned Trish Newport with the medical aid organisation Doctors Without Borders, also known by its French acronym MSF.

“In Ituri, many people already struggle to access healthcare and live with ongoing insecurity, making rapid action critical to prevent the outbreak from escalating further,” she added.

What is Ebola?

Ebola is a severe and often fatal viral disease first identified in 1976 near the Ebola River in what is now the DRC. The virus is believed to originate in wild animals, particularly bats, before spreading to humans.

The disease spreads through direct contact with bodily fluids such as blood, vomit, semen or other contaminated materials, including bedding and clothing. People become contagious once symptoms appear.

Symptoms include fever, vomiting, diarrhoea, intense weakness, muscle pain and, in severe cases, internal and external bleeding. The incubation period can last two to 21 days.

The current outbreak is caused by the Bundibugyo strain, first identified in Uganda in 2007.

It has a “very high lethality rate, which can reach 50 percent”, Kamba said on Saturday. “The Bundibugyo strain has no vaccine, no specific treatment,” he added.

What does the WHO declaration mean?

The WHO’s declaration of a “public health emergency of international concern” is the organisation’s second-highest alert level under international health regulations.

The agency stressed that the outbreak does not currently meet the threshold for a pandemic emergency, the highest level introduced after COVID-19. However, WHO Director-General Tedros Adhanom Ghebreyesus said neighbouring countries were “considered at high risk for further spread due to population mobility, trade and travel linkages, and ongoing epidemiological uncertainty”.

The organisation urged neighbouring countries to activate emergency-management systems, strengthen cross-border screening and isolate confirmed cases immediately. The WHO also recommended daily monitoring of contacts and recommended that exposed individuals avoid international travel for 21 days.

At the same time, the WHO cautioned against border closures, saying restrictions could encourage unmonitored informal crossings and undermine containment efforts.

“There are significant uncertainties to the true number of infected persons and geographic spread associated with this event at the present time,” the WHO said.

“In addition, there is limited understanding of the epidemiological links with known or suspected cases.”

What do we know about past outbreaks?

The DRC has experienced at least 17 Ebola outbreaks since the virus was first discovered there in 1976, making it one of the countries most affected by the disease.

The deadliest Ebola outbreak in the DRC occurred from 2018 to 2020 and killed nearly 2,300 people. Some cases were also reported in Uganda. Another outbreak last year killed at least 34 people before it was declared over in December.

Ebola has killed about 15,000 people since it was discovered, almost all in Africa.

What other challenges is the DRC facing?

A conflict involving several rebel groups is likely to pose a significant challenge to the response to the virus, including in Ituri province.

“The ongoing insecurity, humanitarian crisis, high population mobility, the urban or semiurban nature of the current hotspot and the large network of informal healthcare facilities further compound the risk of spread, as was witnessed during the large Ebola virus disease epidemic in North Kivu and Ituri provinces in 2018-19,” the WHO warned.

This month, an attack by rebels killed at least 69 people in the northeastern province, security officials said.

The mineral-rich region faces ongoing attacks by the Allied Democratic Forces (ADF), a group formed by former Ugandan rebels that has pledged allegiance to ISIL (ISIS), and the Rwanda-backed March 23 Movement, better known as M23.

For more than three decades, the eastern DRC, known for its vast mineral wealth, has been plagued by conflict as numerous armed factions compete to dominate its mining areas.