In its latest update, published Thursday, WHO said hidden chains of transmission are being fuelled by patients who reach advanced stages of the disease without ever receiving care. 

Deaths are still occurring outside health facilities and known transmission chains, while several treatment centres are now overwhelmed.

“Transmission is occurring faster than case detection and isolation, while contact tracing capacities are increasingly strained,” WHO said.

The outbreak remains heavily concentrated in Ituri province, which accounts for roughly 90 per cent of cases and 80 per cent of deaths. The Bunia–Rwampara–Mongbwalu–Nizi corridor remains the main axis of spread, but transmission is also continuing in neighbouring North Kivu, and cases are rising in Haut-Uélé. 

In all, 53 of 140 health zones across five affected provinces have now reported cases.

Congolese authorities reported 4,449 confirmed cases and 2,061 deaths as of Tuesday – a fatality rate of 46 per cent. 

Only 886 patients have recovered. Those numbers put the outbreak on track to potentially become the deadliest Ebola epidemic ever recorded, surpassing the 2014 to 2016 West Africa outbreak, which killed more than 11,000 people among over 28,000 cases.

One indicator is improving: the contact-tracing rate has passed 85 per cent nationally for the first time. 

But the average masks sharp regional gaps – in Haut-Uélé, the rate is only around 58 per cent, which WHO attributed partly to incomplete reporting.

Gaps also persist in alert reporting and in following up confirmed cases, meaning patients can slip through surveillance and sustain chains of transmission that authorities never detect. 

Insecurity and community mistrust are compounding the problem, with some incidents delaying safe burial teams.

WHO said community trust is now central to the response, and urged greater reliance on local leaders and trusted community networks to find cases and contacts, encourage early care-seeking, and ensure safe burials.

Even when patients are found, capacity to treat them is running short. Several treatment and transit centres in Ituri are now “saturated”, WHO said. North Kivu lacks sufficient options to refer patients to specialized facilities, and none of the six affected health zones in Haut-Uélé yet has a treatment centre meeting required standards.

Response teams themselves are under pressure. WHO said delays in paying some response personnel had been reported in several affected zones, warning this “could affect staff motivation and the continuity of response activities, including community engagement and operations at entry and checkpoints.”

The challenge is now twofold: finding the transmission chains still evading surveillance, while urgently expanding capacity to treat those who are found. Until case detection and isolation outpace transmission, better tracing alone will not be enough to turn the epidemic around.