A World Health Organization official said the latest Ebola outbreak in the Democratic Republic of Congo is still spreading largely undetected, with many new cases appearing outside known contact networks.

The WHO Emergencies Director Chikwe Ihekweazu told Reuters that in the heart of the outbreak in Bunia, Ituri province, about 80% of newly confirmed Ebola patients were coming from outside existing lists of known contacts. He added that in some lower-burden areas, such as North Kivu, most new cases were still linked to known contacts—suggesting some progress there, but not enough to prevent wider community transmission.

WHO modelling and test-positivity data indicate the outbreak may be far larger than official counts, potentially two to four times the number of confirmed cases. Government data cited by the report said the outbreak had infected 1,792 people and killed 625 at the time of reporting.

The official also pointed to signs of intense transmission in Ituri, including high positivity among those tested in Bunia. He said preliminary evidence suggests the currently circulating Bundibugyo strain may cause comparatively milder symptoms, which can reduce perceived risk and lead families to care for sick relatives at home before people seek treatment.

That dynamic can increase transmission time in the community, he said, noting patients are “out there much longer than we would like.” Community deaths are also a major concern: analysis of the first 400 deaths found roughly 70% occurred outside treatment centres.

The biggest challenge, Ihekweazu said, is strengthening surveillance. Authorities have begun training large numbers of community health workers to conduct house-to-house visits, identify suspected cases and encourage people with symptoms to seek care