A rapidly growing Ebola outbreak in the Democratic Republic of the Congo has once again placed scientists in a race against time. While the world now possesses approved Ebola treatments and vaccines unimaginable during the devastating West African epidemic a decade ago, the current outbreak is being driven by the far rarer Bundibugyo species of the virus, against which no licensed vaccine or treatment yet exists. As a result, researchers have launched an accelerated programme of clinical trials in an effort to identify effective therapies before the epidemic expands further.
A detailed report published by Die Zeit traces both the scientific progress achieved since the West African crisis and the formidable obstacles that continue to hamper efforts to bring Ebola under control. The story highlights how years of preparation have enabled clinical research to begin far more quickly than in previous outbreaks, while also demonstrating that medical innovation alone cannot halt an epidemic without strong public health systems and community trust.
Few understand that challenge better than Australian physician Amanda Rojek. During the 2014–2016 West African Ebola epidemic, she interrupted her doctoral studies in Global Health at the University of Oxford to lead a clinical trial of an experimental treatment in Sierra Leone. At the time, international researchers were attempting to establish clinical studies while the outbreak was still raging, despite having little agreement on how rigorous research could be conducted under such extreme conditions.
Looking back, Rojek recalls how long it took simply to begin the study. By the time meaningful data became available, the epidemic was already nearing its end. The treatment her team investigated ultimately proved ineffective, leaving her deeply disappointed. The experience later prompted her to redirect her academic research towards improving the way clinical studies are organised during infectious disease emergencies.
More than a decade later, Rojek finds herself confronting another major Ebola crisis. She now co-leads the PARTNERS clinical trial with Congolese researcher Placide Mbala as the Democratic Republic of the Congo battles what the World Health Organization describes as the third-largest Ebola outbreak in history. More than 3,200 cases have already been reported, over 1,400 people have died, and dozens of new infections continue to be confirmed each day. WHO Director-General Tedros Adhanom Ghebreyesus has noted that the outbreak has expanded faster over recent months than any previous Ebola epidemic.
Unlike earlier outbreaks dominated by the Zaire strain of Ebola, the current epidemic involves the Bundibugyo species, a much less common form of the virus that has previously caused only two documented outbreaks. Existing licensed medicines and vaccines target Ebola-Zaire rather than Bundibugyo, forcing researchers to evaluate entirely new therapeutic approaches under emergency conditions.
Years of planning have nevertheless allowed scientists to respond with unprecedented speed. According to Die Zeit, when Congolese authorities officially confirmed the outbreak on 15 May, researchers who had spent years preparing emergency trial protocols convened by video conference the very same evening. They quickly agreed to begin testing two promising treatments: MBP-134, a cocktail of two monoclonal antibodies isolated from the blood of a survivor of the West African Ebola epidemic, and Remdesivir, the antiviral medicine previously used against SARS-CoV-2 and several other viral diseases with mixed success.
Barely six weeks later, on 1 July, the PARTNERS trial began near the outbreak’s epicentre in Bunia. Participants are randomly assigned to one of four treatment groups. One group receives MBP-134, whose antibodies attach to proteins on the surface of Ebola viruses, preventing them from entering human cells. Another receives Remdesivir, which is converted within the body into the molecule GS-443902. The virus mistakenly incorporates this compound while copying its genetic material, interrupting the replication process. A third group receives both medicines, while a fourth receives neither.
A second major study, known as EBO-PEP, began on 15 July and explores a different strategy altogether. Rather than treating infected patients, the trial seeks to prevent disease among people who have had direct contact with Ebola patients or victims. Participants receive the oral antiviral drug Obeldesivir twice daily for ten days. Like Remdesivir, the drug is converted into GS-443902 inside the body, but unlike the intravenous treatments, it is administered as tablets. Researchers hope the approach will function as post-exposure prophylaxis, similar to preventive treatments already used for HIV, rabies and hepatitis B. If successful, experts believe it could fundamentally transform the management of future Ebola outbreaks.
Specialists have praised the remarkable speed with which these studies have been launched. Infectious disease expert Isaac Bogoch describes the rapid deployment of clinical trials as remarkable compared with previous epidemics. Yet the scientific process still requires time. Months will pass before reliable results emerge, and even successful treatments will have only limited impact if the outbreak continues expanding unchecked.
The greatest challenge, researchers warn, lies beyond the laboratory. Ebola outbreaks can, in theory, be contained through rapid diagnosis, isolation of patients and rigorous monitoring of contacts for twenty-one days. When those measures are implemented consistently, transmission chains can be interrupted before the virus spreads further.
Current conditions in the Democratic Republic of the Congo fall well short of that ideal. Many people dying from Ebola are diagnosed only after death, having remained within their communities while receiving care from relatives who frequently become infected themselves. Most newly identified patients also had no known connection to previously confirmed Ebola cases, indicating that numerous transmission chains remain undetected. Public health experts believe the epidemic may therefore be substantially larger than official figures currently indicate.
Several factors have complicated containment efforts. The Bundibugyo strain appears to produce a somewhat slower disease course and lower mortality than the Zaire strain. Although beneficial for individual patients, the slower progression allows infected people to remain mobile for longer periods, increasing opportunities for further transmission. Researchers also believe the outbreak circulated unnoticed for several months before being detected, enabling the virus to spread widely across forty-seven health zones in five provinces.
The geographical and political realities of northeastern Congo further complicate the response. The epidemic is centred in Ituri Province, where armed groups have battled for influence and territory for years. Security concerns restrict access to some communities, while poor infrastructure hampers the movement of medical teams and supplies. Placide Mbala acknowledges that certain areas remain extremely difficult for research and response teams to reach safely.
Perhaps the greatest obstacle, however, is public trust. Communities that have long experienced instability and limited confidence in government institutions are often suspicious of outside intervention. Rumours and conspiracy theories spread rapidly, and recent weeks have seen repeated attacks on clinics and aid workers. Many experts therefore believe the outbreak will continue to expand before meaningful improvements become possible.
Alongside treatment trials, vaccine development is also advancing. The University of Oxford has begun safety testing for the first Bundibugyo-specific vaccine, while additional candidates, including an mRNA vaccine developed by Moderna, are expected to enter testing shortly. The Coalition for Epidemic Preparedness Innovations (CEPI), which funds vaccine development, estimates that even under favourable circumstances these vaccines are unlikely to reach efficacy trials in outbreak areas before the autumn.
Researchers are also exploring whether combining two existing vaccines targeting other Ebola species could provide partial protection against Bundibugyo. Médecins Sans Frontières and its partners are assessing whether such a strategy can be evaluated in the Democratic Republic of the Congo.
Even so, experts caution that neither experimental medicines nor new vaccines will end the outbreak on their own. Public health specialist Craig Spencer, himself an Ebola survivor, argues that outbreaks are ultimately controlled through effective contact tracing and meaningful engagement with affected communities rather than by monoclonal antibodies or ring vaccination alone. Building durable trust with local populations remains a slow and demanding process that cannot be accelerated as easily as launching a clinical trial.
For Amanda Rojek, the availability of experimental treatments at least offers patients hope that did not exist during earlier epidemics. Many people have welcomed the possibility of receiving potentially lifesaving therapies, even as uncertainty remains about their effectiveness. Yet she harbours few illusions about the scale of the challenge ahead. As Die Zeit reports, despite remarkable scientific progress and unprecedented research preparedness, the outbreak remains exceptionally difficult to control, and researchers expect it to become larger and persist for considerably longer before it is finally brought under control.
