Bundibugyo Ebola – A new study in *The Lancet Infectious Diseases* tries to pin down the scale of the ongoing Ebola outbreak in the Democratic Republic of the Congo, caused by the rare Bundibugyo virus. As of June 13, the country reported 782 confirmed cases and at least 181 dea
By the time alarm bells rang for this Ebola outbreak in the Democratic Republic of the Congo, it was already larger than public health teams were prepared to see.
The outbreak—driven by the rare Bundibugyo virus—is now the third largest on record. It has already produced 782 confirmed cases and at least 181 deaths as of June 13. according to the reporting in the new study. Suspected infections and deaths are higher. Most cases are in the DRC’s province of Ituri. but infections have also been recorded elsewhere in the country. and in neighboring Uganda.
What makes the situation especially worrying is how different it is from prior Ebola epidemics. Bundibugyo has been less understood, with only two outbreaks previously. There are no approved vaccines or treatments for this kind of Ebola, though several vaccine candidates are in development. And crucially, the outbreak went undetected for some time, giving it the chance to grow quickly.
Ruth McCabe, a public health researcher who conducted the research while at the School of Public Health at Imperial College London, said the timing of detection is part of what changed the stakes.
“[T]he reason why alarm bells really rang at the beginning of this [outbreak] was the size that it was at the time of detection,” she said.
Compared with previous Ebola outbreaks, she added, “this was detected late, and that is alarming.”
McCabe is a co-author of a study published last week in *The Lancet Infectious Diseases* that aims to estimate the outbreak’s size under different assumptions—assumptions about levels of testing, infection growth, and the fatality rate of the Bundibugyo virus.
The challenge is that tracking Ebola is notoriously hard. Weak public health systems, armed conflict, and other disruption can all distort what counts as a case and what counts as a death. Those gaps make it difficult to compare the current outbreak’s numbers with past Ebola epidemics.
To estimate how widespread the outbreak might be, the researchers used two different approaches that—by design—shouldn’t rely on the same blind spots.
In one model, they looked at suspected and confirmed deaths reported as of May 27. They assumed a time period from symptom onset to death of 11.37 days. Because the actual fatality rate for Bundibugyo isn’t clear. the authors ran three scenarios using fatality rates of 26 percent. 33 percent. and 40 percent. They also tested different growth patterns, pairing moderate, fast and slow growth with doubling times of 10, seven, and 14 days, respectively.
In the second model, the starting point wasn’t deaths—it was where the virus traveled. Researchers focused on geographic spread tied to people moving across the border from the DRC’s provinces of Ituri and Nord Kivu into Uganda. They based the calculations on three confirmed imported cases of Ebola reported in Uganda as of May 27. Again. they ran moderate. fast and slow growth scenarios. but this time they varied what they assumed about where the imported cases came from—either from Ituri alone or from both Ituri and Nord Kivu.
Despite coming from different kinds of data, the models pointed in the same general direction. The first approach produced an estimate of between 306 and 2,521 cases as of May 27. The geographic spread approach estimated between 282 and 1,345 cases. The authors stress that these figures come with substantial uncertainty and that many cases could be missed.
“The broad convergence of our estimates from two independent methods supports the conclusion of potentially substantial underdetection of cases and the potential for wider transmission,” the authors wrote in the study.
The methods also underline what McCabe believes researchers still need most: better basic information about how easily Bundibugyo spreads. Without that, it’s hard to say how long the outbreak could last or how far it could go.
To better understand how big the current outbreak could get and how long it might last, McCabe said researchers need more accurate information about how transmissible the virus is, adding, “That is the next step.”
For communities in Ituri and beyond, the timing is already a grim lesson. When an Ebola outbreak is detected late—and when the virus involved is one of the least understood forms—modeling the scale becomes less an academic exercise and more a race against silence and missed cases. The question now isn’t just how many people are sick today. It’s how many infections slipped through the system before anyone could measure the outbreak at all.
Ebola Democratic Republic of the Congo Bundibugyo virus Ituri Uganda Lancet Infectious Diseases outbreak modeling underdetection public health