The Ebola outbreak in the Democratic Republic of Congo may be spreading largely undetected, with the true number of infections potentially two to four times higher than official figures, a senior World Health Organization official has warned.
The outbreak in the country’s northeast has so far infected 1,792 people and killed 625, according to government data released Thursday. Most cases remain concentrated in Ituri province, where health workers are struggling to trace infections and contain transmission.
Chikwe Ihekweazu, WHO’s emergencies director, said four out of every five newly confirmed Ebola patients in the outbreak’s epicentre in Bunia, Ituri’s capital, were not on existing contact lists.
“Eighty percent of the new patients confirmed are coming outside of known contact lists,” Ihekweazu told Reuters in an interview late Thursday.
He said the situation was more encouraging in areas with fewer cases, including North Kivu, where nearly all new infections were linked to known contacts.
The outbreak, declared in mid-May, is being driven by the Bundibugyo strain of the Ebola virus. WHO modelling and test positivity rates suggest the actual scale of the outbreak could be two to four times larger than the confirmed case count.
Around 90% of reported cases are in Ituri, particularly in Bunia, Rwampara, Mongbwalu and Nyakunde health zones, where community transmission remains intense. In Bunia, a city of about one million people, roughly half of those tested for Ebola are returning positive results.
The virus has also spread to North Kivu, South Kivu and, more recently, Tshopo province.
WHO officials say the Bundibugyo strain may cause milder symptoms than other Ebola variants, which could be making communities less likely to seek treatment quickly. Families may care for sick relatives at home before approaching health centres, allowing infected people to remain in the community longer.
“Patients are out there much longer than we would like,” Ihekweazu said. “The longer patients are outside of care, the more likely they are to transmit this illness.”
Deaths outside treatment centres remain a major concern. WHO analysis of the first 400 deaths found that about 70% occurred outside formal care facilities.
Ihekweazu said improving surveillance is now the biggest challenge for the response. Authorities this week began training 21,000 community health workers to carry out house-to-house visits, identify suspected infections and encourage people with symptoms to seek treatment.