A new study says the Ebola outbreak in eastern Democratic Republic of the Congo began with an independent animal-to-human transmission, rather than a virus variant carried over from earlier outbreaks. More than 2,000 people have died among 4,449 recorded cases, making it the fastest-moving Ebola outbreak on record.
Researchers found that the outbreak’s Bundibugyo virus is genetically distinct from strains seen in outbreaks in 2007 and 2012. The animal source has not been identified, and scientists say transmission after the initial spillover has been predominantly from person to person.
What researchers found
The Nature Medicine study analysed genetic samples from 22 patients in the DRC and Uganda. Its findings indicate that the virus crossed independently from an animal reservoir into a person before spreading through human transmission. The Ugandan outbreak was linked to the outbreak in the DRC.
The finding does not mean that a new form of Ebola has suddenly appeared or that animals have begun transmitting the virus in a fundamentally different way. The Bundibugyo strain is rare, and no vaccine has yet been developed for it.
Related coverage: WHO warns DR Congo Ebola crisis is spreading beyond containment.
How the outbreak developed
The outbreak was formally declared on May 15, but genetic sequencing later showed that the virus had been circulating since February. The delay allowed multiple chains of transmission to become established before the outbreak was recognised.
The World Health Organization said on Wednesday that the outbreak was spreading faster than health authorities could contain it and was on track to become the deadliest Ebola outbreak on record. A moderate projection puts its peak within six months; under a more severe scenario, it could continue for nine to 12 months.
Treatment and containment challenges
The animal origin does not change how patients are treated. Care focuses on fluid and electrolyte management, treating shock and organ dysfunction, managing co-infections and evaluating investigational therapies. The Bundibugyo virus does not have the same licensed, proven virus-specific therapeutics available for Zaire ebolavirus.
More context: UN Calls for Accelerated Action to Contain Ebola Spread in DR Congo Amid Complex Crisis.
Researchers say decentralised laboratory diagnostics, genomic sequencing and faster detection could help identify future outbreaks earlier. Experimental vaccines and treatments specifically targeting circulating Bundibugyo strains are in clinical development, but no licensed vaccine or treatment is currently available for the strain.
The response has been complicated by strikes by unpaid health workers, misinformation and burial practices that can increase transmission risk. More than 100 health workers have been infected and about 35 have died. The World Health Organization said 12 tonnes of medical supplies, including personal protective equipment and sampling materials, had been sent to the DRC, with another six tonnes arriving.
Measures beyond the DRC
Neighbouring countries and other governments have introduced travel and health measures. Rwanda has restricted entry for foreign travellers who had been in the DRC during the previous 30 days, while the United States warned that people who had been in the DRC within 21 days before departure would not be allowed to board commercial flights to US destinations.
Also read: DRC Ebola outbreak started in February, WHO says.
Bahrain suspended entry for 30 days for foreign travellers arriving from South Sudan, the DRC and Uganda. Governments in Asia have also begun border screening and strengthened quarantine preparedness.
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