Congo Ebola outbreak surpasses 2,000 deaths as unseen Bundibugyo variant spreads undetected for months

Outbreak scale and speed

The Democratic Republic of Congo's 17th Ebola outbreak has reached 4,449 confirmed cases with 2,061 deaths as of late Tuesday, according to government data. Earlier the same day, authorities had reported 4,381 cases and 2,011 deaths. The case fatality rate stands at 45.9%, exceeding the 39.6% rate recorded during the 2014-2016 West Africa outbreak. The first 1,000 deaths were recorded over nine weeks, but the second 1,000 took just three weeks. The outbreak is now the second largest in history, behind only the West Africa epidemic that recorded 28,616 cases and 11,310 deaths across Guinea, Liberia and Sierra Leone. It is approaching the toll of the 2018-2020 DRC outbreak, which recorded nearly 2,300 deaths among 3,500 confirmed cases.

Delayed detection and a new variant

The WHO has determined through genetic sequencing that the outbreak actually began in February, three months before it was officially declared on 15 May. Early cases were wrongly attributed to malaria, typhoid and more common Ebola types, contributing to diagnostic delays. A study published Monday in Nature Medicine by researchers from Congo, Uganda, Belgium and other countries analysed virus samples from 22 patients and found that the strain responsible is a previously unseen variant of the rare Bundibugyo species, genetically distinct from Bundibugyo viruses identified in outbreaks in 2007 and 2012. The findings indicate the outbreak began with a new transmission from animals to humans, though the animal source has not been identified. Genetic analysis also confirmed that cases detected in Uganda are linked to the Congo outbreak.

This strain probably began circulating as early as January, but was not detected or confirmed before April-May, which gave the virus time to infiltrate communities. Since then, we have had difficulty keeping up with the pace of its spread.

Response challenges on the ground

The WHO has declared the outbreak a public health emergency of international concern. It has spread across five provinces and crossed into neighbouring Uganda. Most new cases continue to be recorded outside monitored contact groups, a sign that transmission remains uncontained. WHO Regional Director for Africa Mohamed Yakub Janabi said response teams are reaching only 30% of infected people, while 70% die at home.

We are chasing the virus, but the virus is ahead of us.

Armed conflict, poor road conditions and health worker strikes over unpaid wages have hampered delivery of aid to remote areas. Between April and June, there was a 42% drop in the use of essential health services in outbreak hotspots. UNICEF representative John Agbor reported that one facility that previously saw 500 patients per month had dropped to almost nothing. More than two-thirds of Ebola deaths are happening in the community rather than in treatment centres, and patients often arrive at clinics in Bunia too late for effective care.

Vaccine and treatment outlook

No approved vaccines or treatments exist for the Bundibugyo species. WHO experts recommended on 7 August evaluating the Ervebo vaccine, approved for the Zaire strain, in a phase 3 clinical trial against Bundibugyo. The global Ebola vaccine stockpile, created and funded by Gavi and produced by Merck, holds approximately 500,000 doses, some already kept in the DRC. Gavi director Sania Nishtar warned the outbreak could become the largest ever recorded worldwide. Congolese Health Minister Samuel Roger Kamba said the peak has not yet been reached but expressed hope that within three months the spread would be controlled and case numbers would begin to decline.