The Democratic Republic of Congo has confirmed more Ebola outbreaks than any other country in the world. As of 2025, that number stood at fourteen separate events since the virus was first isolated from a sample taken near the Ebola River in 1976. Each outbreak begins the same way: fever appears in a rural area, diagnosis is delayed by days or weeks, and by then the contact network has already expanded beyond easy reach. Each one is also different, and that difference matters enormously for whether the tools we have can actually work.
The situation in 2026 continues this pattern. WHO has activated outbreak response protocols as it has done repeatedly in recent years. The virus has not changed fundamentally. What has changed is how much we know about stopping it, and how unevenly we apply that knowledge.
What you need to know about Ebola strains
Ebola is not one virus. The genus Orthoebolavirus includes six identified species, of which two are responsible for most human outbreaks: the Zaire strain (Orthoebolavirus zairense) and the Sudan strain (Orthoebolavirus sudanense). This distinction matters because the tools that exist to fight one do not automatically work against the other.
The licensed vaccine, rVSV-ZEBOV (marketed as Ervebo and approved by the FDA in December 2019), targets the Zaire strain. In the DRC’s 2018–2020 North Kivu/Ituri outbreak, 3,470 people were infected and 2,287 died. Ring vaccination with Ervebo was part of the response. The outbreak eventually ended, but it took nearly two years, partly because active armed conflict in the region disrupted contact tracing and safe burial practices.
When Uganda experienced a Sudan-strain outbreak in September 2022, there was no licensed vaccine to deploy. Fifty-five people died. Experimental candidates were rushed into trials. None were ready in time.
The vaccine that works, and when
The strongest evidence for Ebola vaccination comes from Guinea in 2015. Anne-Marie Henao-Restrepo and colleagues, writing in The Lancet in 2017, reported results from the rVSV-ZEBOV ring vaccination trial: among 3,775 people vaccinated immediately after contact with a confirmed case, there were zero Ebola cases in the 10 days following vaccination. Among those randomised to delayed vaccination, there were 16 cases. The study had an unconventional design and the authors were candid about its limitations. But the effect size was striking enough that the trial was stopped early and the vaccine was offered to all participants.
Ring vaccination works by building a protective circle around each confirmed case: vaccinate every identified contact, then their contacts in turn. Done quickly, with high tracing coverage, it interrupts transmission chains before they can spread. The problem is that doing it quickly requires knowing where cases are, which requires healthcare workers trusted by communities, which requires a health system with some minimal infrastructure.
In parts of eastern DRC, that infrastructure has been actively weakened by conflict for years.
Why geography keeps complicating everything
I keep returning to the 2018–2020 DRC outbreak when I think about why Ebola containment fails. There was a licensed vaccine. Experienced response teams were in place. And there were still 3,470 cases.
The WHO’s after-action reviews identified the same factor repeatedly: active armed groups in North Kivu attacked health facilities and killed response workers, making consistent surveillance impossible. Communities, for reasons that are entirely rational given their experience with those same institutions, sometimes refused vaccination or kept sick relatives away from health authorities.
The technical problem of Ebola containment was largely solved in 2015. What remains is a political and systems problem.
Where the science is now
Multiple Sudan-strain vaccine candidates are in development. As of 2025, a chimpanzee adenovirus-vectored candidate developed with involvement of the Jenner Institute at Oxford was in later-phase trials, and an mRNA candidate had entered human studies. Neither had yet cleared the licensing threshold that Ervebo cleared in 2019.
There is also growing recognition in outbreak modeling work that the ring vaccination strategy, designed for contained rural outbreaks, may not scale simply to urban settings. An Ebola cluster in a city of 15 to 17 million people, with the population density and health system constraints typical of major Central African cities, would require a response that is categorically larger than anything previously mounted. The planning documents exist. The financing commitments do not match them.
The gap between knowing what to do and being resourced to do it in a conflict zone is not a knowledge problem.
What would actually help
For the 2026 outbreak, the evidence points to the same set of needs it has always pointed to. Early case detection depends on community health workers trusted by the people they serve and paid reliably enough to stay on the job. Contact tracing requires secure access to affected areas. Safe burial depends on community leaders who have been genuinely consulted, not simply informed of decisions already made.
At the global level, the absence of a licensed Sudan-strain vaccine in 2026, more than three years after the Uganda outbreak exposed that gap, reflects something specific about how pandemic preparedness is financed. Vaccines with small commercial markets attract limited private investment. The Coalition for Epidemic Preparedness Innovations has funded Sudan-strain candidates, but development timelines have extended. What the 2022 Uganda outbreak showed is that the gap between “candidate exists” and “vaccine is licensed and stockpiled” is measured not just in science but in money and political priority.
The Ebola virus has been known for fifty years. Each new outbreak adds a data point to a pattern that is not ambiguous: we know enough to stop this, and we keep not quite committing to it.
This article is for educational purposes only and does not constitute medical advice, diagnosis, or treatment recommendations. Consult a qualified healthcare provider for any health concerns. See our Medical Disclaimer.
Sources
- Henao-Restrepo AM, Camacho A, Longini IM, et al. Efficacy and effectiveness of an rVSV-vectored vaccine in preventing Ebola virus disease: final results from the Guinea ring vaccination, open-label, cluster-randomised trial (Ebola Ça Suffit!). Lancet. 2017;389(10068):505–518. PMID: 28017403.
- World Health Organization. Ebola virus disease — Democratic Republic of the Congo. External situation reports. 2018–2020. who.int
- World Health Organization. Sudan virus disease — Uganda. Disease Outbreak News. 2022. who.int
- U.S. Food and Drug Administration. FDA approves first vaccine for the prevention of Ebola virus disease. December 19, 2019. fda.gov
- Coalition for Epidemic Preparedness Innovations (CEPI). Ebola Sudan programme overview. 2023. cepi.net
- World Health Organization. Ebola virus disease — fact sheet. Updated 2024. who.int
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