Health authorities reported 550 confirmed cases as of Sunday, including 101 deaths and 19 recoveries, according to the latest situation update released late Monday. The outbreak was officially declared on May 15.

The vast majority of infections have been recorded in Ituri province, which accounts for more than 90 percent of confirmed cases. Additional cases have been identified in North Kivu and South Kivu provinces, while the virus has also crossed into neighboring Uganda.

Officials believe the true number of infections may be higher because the outbreak was detected weeks after transmission had already begun. Response efforts have been further complicated by the absence of an approved vaccine or treatment for the strain responsible for the current outbreak.

The outbreak has been linked to the rare Bundibugyo strain of Ebola virus, for which no approved vaccine or therapeutic treatment currently exists. This differs from the Zaire strain, which was responsible for most of Congo’s previous Ebola outbreaks and for which vaccines and treatments have been developed.

Authorities said the sharp increase in confirmed infections partly reflects expanded diagnostic capacity, which has enabled laboratories to process a backlog of previously collected samples.

Health workers operating in affected areas continue to face significant obstacles. Medical teams have been attacked on multiple occasions by residents frustrated by the outbreak response, while persistent skepticism among some communities has complicated surveillance and containment efforts.

Security concerns remain a major challenge across eastern Congo, where numerous armed groups continue to operate. Ongoing violence has limited access to several affected communities and disrupted disease-monitoring activities.

The World Health Organization said Monday that insecurity is restricting access for response teams, hindering surveillance operations and increasing the risk that new chains of transmission could go undetected.

The agency said the attacks on health personnel underscore the difficulties of responding to a public health emergency in conflict-affected areas and highlighted the importance of cooperation with local leaders and communities.

Eastern Congo has experienced repeated outbreaks of Ebola over the past decade, but health officials warn that the combination of armed conflict, delayed detection and the lack of approved medical countermeasures for the Bundibugyo strain presents a particularly complex challenge for containment efforts.

The newly identified cases include a Ugandan driver who transported the country’s first confirmed Ebola patient and a healthcare worker who was exposed to the virus while caring for the same individual, the ministry said in a statement.

A Congolese woman was also confirmed to have contracted the disease, bringing the cumulative number of confirmed infections to five.

Health authorities did not immediately provide additional details on the conditions of the patients or whether further contacts were being monitored. The latest infections underscore the risks faced by frontline medical personnel and individuals who come into close contact with infected patients during outbreak investigations.

Uganda has previously experienced several Ebola outbreaks and has developed response mechanisms that include contact tracing, patient isolation and public health surveillance aimed at limiting transmission.

The confirmation of additional cases is likely to heighten monitoring efforts by health officials as they seek to prevent wider community spread and identify potential chains of transmission linked to the initial patient.

Ebola is a severe viral hemorrhagic disease transmitted through direct contact with the bodily fluids of infected individuals or contaminated materials. Outbreaks require rapid detection and containment measures to prevent further spread.

The WHO said the outbreak did not yet meet the threshold for a pandemic emergency but warned that countries bordering Congo faced a heightened risk of further spread as infections expanded across eastern regions and new cases emerged in Uganda’s capital, Kampala.

According to the agency, 80 suspected deaths, eight laboratory-confirmed cases and 246 suspected infections had been reported as of Saturday in Congo’s Ituri province, particularly in the health zones of Bunia, Rwampara and Mongbwalu.

The Congolese health ministry had earlier confirmed that at least 80 people had died in the outbreak, which health officials believe may be significantly larger than currently documented because of high positivity rates in early testing and increasing numbers of suspected infections.

The outbreak involves the Bundibugyo strain of Ebola virus disease, a rarer variant for which no approved vaccines or targeted therapeutics currently exist, unlike the more common Ebola-Zaire strain that has been the focus of previous immunization campaigns in Central Africa.

The WHO described the situation as “extraordinary,” warning that international transmission had already been documented.

In Kampala, two unrelated laboratory-confirmed Ebola cases, including one death, were identified on Friday and Saturday in travelers arriving from Congo, according to the agency. A confirmed case was also detected in Kinshasa involving a traveler returning from Ituri province.

The WHO urged governments to activate national emergency-response systems, intensify border screening and strengthen surveillance along internal transportation routes to contain further spread.
The agency also advised that confirmed Ebola patients and close contacts should avoid international travel except for medical evacuation purposes.

It recommended immediate isolation of confirmed cases, daily monitoring of contacts and restrictions on domestic travel for exposed individuals until 21 days after potential infection.

At the same time, the WHO cautioned governments against shutting borders or imposing sweeping trade restrictions, warning that such measures could push movement across unofficial crossings beyond the reach of health monitoring systems.

The outbreak poses an additional challenge for regional health systems already strained by conflict, population displacement and limited medical infrastructure in eastern Congo, where previous Ebola epidemics have repeatedly tested emergency response capacities.