The Ebola outbreak in the Democratic Republic of Congo could be three times larger than official figures, with only an estimated 30 to 40% of infections currently being detected, the Africa Centres for Disease Control and Prevention (Africa CDC) has warned.
The agency said the outbreak had so far recorded 5,105 confirmed cases and 2,420 deaths, giving a case fatality ratio of about 47%.
A total of 1,081 recoveries have been reported, while 762 patients were in isolation, according to figures presented during an Africa CDC briefing on Thursday.
Yap Boum II, head of the emergency preparedness and response division at the Africa CDC, said modelling by researchers from the DRC, Imperial College London and other partners suggested the actual size of the outbreak could be significantly higher because many infections are being missed.
"We can say that between 30 to 40% of the cases are actually detected," Yap Boum II said, adding that the outbreak "could be three times the current size in the number of confirmed cases".
The agency said the difficulty in detecting infections was partly linked to the nature of the Bundibugyo virus, which causes symptoms that can be less severe or different from those associated with the Zaire ebolavirus.
Less than 3% of cases were reported among known contacts, while fewer than 40% had an epidemiological link to a confirmed case, the briefing heard.
The response is also being complicated by a high number of deaths occurring outside Ebola treatment centres.
Africa CDC said about 97% of reported deaths were occurring in the community, including people dying at home or in health facilities without specialised Ebola treatment and infection prevention measures.
"At least 97% of deaths are reported in the community," Yap Boum II said, stressing that the response needed to reduce community deaths to zero.
Community surveillance also remains weak, with only about 20% of alerts originating from communities, according to the agency.
Africa CDC said this was making contact tracing difficult, with only about 10 contacts identified for every confirmed case, compared with 21 contacts per case during Uganda's outbreak and 57 contacts per case in the DRC's 2018-2020 response.
"You can miss the case in the village because they don't meet the case definition, but you cannot miss the death in the village," the official said.
The outbreak has spread across several provinces, with Ituri remaining a major epicentre. Two recent cases were also reported in Bas-Uele, near the Central African Republic border, prompting increased cross-border surveillance.
Despite the challenges, Africa CDC said three health zones had gone more than 42 days without a confirmed case, while five others had passed 21 days without new infections.
Officials said improved laboratory capacity and faster testing, together with stronger community engagement, would be critical to containing the outbreak.