Africa CDC warns Congo's Bundibugyo Ebola outbreak is spreading beyond Ituri epicenter

The Ebola outbreak caused by Bundibugyo virus in the Democratic Republic of the Congo has become the largest Ebola outbreak ever recorded in the country, irrespective of species, and the second largest on record anywhere. The epidemic has reached 61 health zones spread across six of the country's 26 provinces, and the agencies leading the response say it is no longer confined to the province where it began.

The Africa Centres for Disease Control and Prevention reported on September 10 that the outbreak is rapidly spreading beyond Ituri province, telling its weekly briefing that the latest government figures released the same day showed 6,843 cases, including 3,310 deaths. Officials described a shifting geography: new cases and deaths have declined in recent weeks in Ituri, the epicentre, but have risen sharply in neighbouring North Kivu and Haut-Uele.

The outbreak was declared in May. The World Health Organization reported on September 10 that it is unfolding in a complex humanitarian setting marked by insecurity, armed conflict and displacement, with more than 26 million people acutely food insecure in the region. The first known case was a patient who died on April 20 in Mongbwalu, a mining town in Ituri, according to WHO. This is the second documented Bundibugyo outbreak in the DRC, after 2012, and Bundibugyo virus is a species for which no vaccine and no specific treatment have been licensed.

Against that backdrop, the DRC began vaccinating front line workers last month with Ervebo, a Merck vaccine licensed against the Zaire species of Ebola virus rather than the Bundibugyo species circulating now. Approximately 2,000 front line workers have received the shot so far, WHO told Healio, and the campaign has concentrated on newly affected provinces rather than on the epicentre itself.

Key Facts

The World Health Organization reported on September 10 that its Disease Outbreak News update counted 6,757 confirmed cases and 3,267 deaths in the DRC as of September 7, a crude case fatality ratio of 48.3 percent. Cumulatively that includes 20 confirmed cases in Uganda and one in France, for 6,778 confirmed cases and 3,269 deaths overall, with at least 1,611 patients recovered, most of them in the DRC. Since the previous update on August 28, an additional 963 confirmed cases and 481 confirmed deaths were reported in the country, a rise that WHO attributes both to strengthened surveillance and to sustained community transmission and geographic expansion.

Ituri remains the epicentre with 5,406 cases, including 1,114 in the previous 21 days. North Kivu is second with 1,066 cases and has recorded one of the highest case fatality ratios of the outbreak, at 65.4 percent. The spread is still widening: since the August 28 update the virus reached one additional health zone, Kayna, in North Kivu, bringing the total to 61 affected health zones across Bas-Uele, Haut-Uele, Ituri, North Kivu, South Kivu and Tshopo. In the 24 hours before September 7, 71 new confirmed cases were reported from 17 health zones in Ituri, North Kivu and Haut-Uele, and 21,359 of 24,719 registered contacts, or 85.3 percent, were monitored.

The Associated Press reported on September 10 that new cases in North Kivu more than doubled to 381 in the latest three week period, from 165 in the earlier period, according to Yap Boum, Africa CDC's head of emergency preparedness and response. The virus recently reached two more health zones in North Kivu, where fighting with Rwanda backed M23 rebels has complicated the response.

Healio reported on September 10 that the DRC holds a stockpile of about 70,000 doses of Ervebo, of which 50,000 are intended for front line workers and 20,000 for a WHO led phase 3 trial testing whether the vaccine works against Bundibugyo ebolavirus. As of September 6, 2,007 people had been vaccinated across six health zones in Tshopo, Bas-Uele and Ituri, according to WHO. The front line workers who received Ervebo are working in Tshopo and Bas-Uele, not Ituri.

Placide Mbala Kingebeni, Africa CDC's director for research and innovation, said clinical trials are under way to find a licensed vaccine for the Bundibugyo virus, starting in the eastern provinces of Tshopo, Haut-Uele and Bas-Uele, and that vaccinations in Ituri are set to start next week. Doses remain a key constraint: Congo has received 70,000 doses so far. Two further candidates are in early testing, with Oxford running a phase 1 trial of an experimental Bundibugyo vaccine known as ChAdOx1 BDBV and Moderna testing an mRNA vaccine designated mRNA-1469.

Analysis

The numbers make the direction of travel plain. An outbreak that took 40 days to eclipse 1,000 cases, compared with 235 days for the 2018 to 2020 outbreak, is now adding hundreds of confirmed cases a week and has crossed into a province whose case fatality ratio of 65.4 percent is far above the national figure of 48.3 percent. The bigger picture here is that the response is being asked to do two difficult things at once: chase a fast moving virus across a widening map, and generate the scientific evidence for a vaccine that does not yet exist for this species, all inside an active conflict zone.

The Ervebo campaign is the clearest illustration of that tension. The vaccine is safe and effective against Ebola virus disease, but WHO has been explicit that it is not known whether it provides protection against the Bundibugyo virus in humans, which is why the agency recommends its use only within a research protocol. Laboratory testing of serum samples published in The New England Journal of Medicine suggests the vaccine may offer cross protection against Bundibugyo, and early nonclinical data point the same way. That is a promising signal, but it is not proof, and the trial that would supply proof may not report for months.

Jennifer B. Nuzzo, director of the Pandemic Center at Brown University, called the phase 3 trial encouraging but warned that the outbreak is moving too quickly to wait for the results of a vaccine trial. Her point cuts to the core of the problem: the tools that normally bend an Ebola curve, a licensed vaccine and specific treatments, are unavailable for this species, so the response is falling back on surveillance, contact tracing and classic outbreak control in terrain where displacement and armed conflict keep breaking the chains of transmission.

WHO says the outbreak remains out of control and is on track to surpass the 2014 to 2016 West Africa outbreak, the deadliest on record, which killed more than 11,000 people in Guinea, Liberia and Sierra Leone. That comparison should be handled carefully, since the two epidemics differ in geography, population density and health system capacity. Even so, the trajectory is serious enough that Africa CDC used its weekly briefing to flag geographic spread rather than to announce containment.

Why It Matters

Bundibugyo virus is a rare species with no licensed vaccine and no specific treatment, which means every case is managed with supportive care alone. The DRC has now reported a larger Ebola outbreak than any in its history, and the cumulative toll of 6,778 confirmed cases and 3,269 deaths across the DRC, Uganda and France shows how quickly a regional outbreak becomes an international one. Uganda's 20 cases and France's single case are reminders that pathogens do not respect provincial or national borders.

The operational picture compounds the biological one. More than 26 million people in the region are acutely food insecure, insecurity and displacement are driving intense population movements, and in North Kivu the response is unfolding alongside fighting with Rwanda backed M23 rebels. Contact tracing is running at 85.3 percent of registered contacts monitored in a 24 hour window, a figure that is strong by the standards of many outbreaks but still leaves roughly one in seven contacts unmonitored in a fast growing epidemic.

Vaccine supply and vaccine science are the binding constraints going forward. Of the 70,000 doses on hand, 50,000 are earmarked for front line workers and 20,000 for a trial that has not yet begun in earnest. WHO has said the Ervebo trial could start in October or November, but that it may take months to determine whether the vaccine protects against Bundibugyo.

Next Up

The immediate test is geographic. Vaccinations in Ituri, the province with 5,406 cases and the largest burden of transmission, are set to start next week, while the WHO led phase 3 trial of Ervebo against Bundibugyo ebolavirus is expected to begin in October or November. Africa CDC has said the campaign initially targeted the newly affected provinces, and how quickly the effort reaches Ituri and North Kivu will shape whether the doubling of cases seen in North Kivu continues.

Further out, the outbreak's course depends on three variables that no single agency controls: whether the Oxford phase 1 trial of ChAdOx1 BDBV and Moderna's mRNA-1469 testing produce a licensable Bundibugyo vaccine, whether the security situation in North Kivu allows responders to reach affected health zones, and whether the 70,000 doses already in the country are enough to cover the front line workers and contacts who need them.