A vaccine's job is to keep people alive, not necessarily to prevent all symptoms.
In the forests of Central Africa, a virus older than its name is outpacing the tools built to stop it. The Bundibugyo strain of Ebola — killing between three and five of every ten it infects — has claimed 61 lives across the Democratic Republic of the Congo and Uganda, while the vaccines designed for its better-known cousin offer little protection against it. Scientists at Oxford are now racing to close that gap, but the delay in identifying the strain, the absence of commercial incentive, and the fragility of healthcare infrastructure in outbreak zones remind us that preparedness is not a technical problem alone — it is a question of what humanity chooses to prioritize before the crisis arrives.
- A misidentified pathogen cost precious weeks at the outbreak's start, allowing Bundibugyo Ebola to spread far beyond what early intervention might have contained.
- With a 30–50% fatality rate and no approved vaccine, every confirmed case among the 359 on record carries odds that most diseases in the modern world no longer impose.
- The two licensed Ebola vaccines — both targeting the Zaire strain — share only about 60% genetic similarity with Bundibugyo's surface protein, offering little cross-protection and leaving a critical immunological gap.
- Oxford's Teresa Lambe and Rebecca Makinson are advancing a ChAdOx-based vaccine candidate, but funding, manufacturing logistics, and vaccine skepticism in under-resourced regions threaten to slow delivery even if the science succeeds.
- Contact tracing is already breaking down in areas with weak infrastructure, while climate change and habitat encroachment raise the likelihood that Bundibugyo will not be the last unknown strain to spill from animal reservoirs into human communities.
Sixty-one people have died. Three hundred fifty-nine cases are confirmed. The virus responsible is Bundibugyo Ebola — a strain that kills between three and five of every ten it infects — and no approved vaccine exists to stop it.
The outbreak is active now across the Democratic Republic of the Congo and Uganda. Oxford scientists Teresa Lambe and Rebecca Makinson are among those working urgently toward a vaccine, backed by recent funding from the Coalition for Epidemic Preparedness Innovations. But the response began at a disadvantage: early diagnostic tests were run against the wrong virus entirely. By the time Bundibugyo was correctly identified, the window for early containment had closed.
Bundibugyo belongs to the same viral family as the better-known Zaire strain, first appearing in Uganda's Bundibugyo district in 2007. Fruit bats are the leading suspect as its animal reservoir, though the precise mechanics of spillover into humans remain poorly understood. Crucially, Bundibugyo's surface glycoprotein — the structure the immune system learns to target — shares only about 60% similarity with Zaire's. The two licensed Zaire vaccines appear to offer limited cross-protection, though human trials have not yet been possible.
The deeper obstacle is not scientific but economic. Ebola outbreaks, though devastating, are rare and geographically concentrated. Pharmaceutical companies see no viable market. Development costs millions; commercial returns are negligible. Progress has depended on governments and nonprofits, and the strains causing larger outbreaks were naturally prioritized first. Lambe's team works with a platform called ChAdOx — a chimpanzee adenovirus modified to deliver the Ebola glycoprotein — which is proven and adaptable, but only effective if it reaches people in time.
On the ground, contact tracing is already faltering. Infrastructure gaps make it nearly impossible to track every exposure in affected communities. Vaccine skepticism adds another layer of difficulty, and Lambe has stressed the importance of honest communication — making clear what a vaccine can and cannot do, a lesson imperfectly learned during the Covid pandemic.
Looking further out, the conditions producing outbreaks like this one are intensifying. Climate change is shifting animal habitats and viral circulation patterns. Human encroachment into wildlife zones increases spillover risk. Scientists surveying bat populations warn that other unidentified strains almost certainly exist. The race to develop a Bundibugyo vaccine is urgent — but those working on it understand it is also part of a longer, unfinished effort.
Sixty-one people are dead. Three hundred fifty-nine confirmed cases. The virus killing them is Bundibugyo Ebola, a strain that kills between three and five of every ten people it infects, and for which no vaccine exists.
The outbreak is spreading across the Democratic Republic of the Congo and Uganda right now. Two scientists at Oxford—Teresa Lambe and Rebecca Makinson—are among those racing to build protection against it. In early June, Oxford received funding from the Coalition for Epidemic Preparedness Innovations to join the effort. But the clock is running differently this time. The initial tests, Makinson explained, were done on the wrong virus entirely. By the time anyone realized Bundibugyo was the culprit, the moment to catch the outbreak early had already passed. Cases climbed higher than they should have. Public health measures scrambled to catch up.
Bundibugyo is one species within a larger family of Ebola viruses. It was first identified in 2007 in Uganda's Bundibugyo district. Like its cousins, it almost certainly lives in animals—fruit bats are the leading suspect—and occasionally jumps into humans. But the details of how it behaves, where it hides, what triggers spillover: much of that remains unknown. The virus is thread-like under a microscope, shaped like a shepherd's crook, with a surface protein called glycoprotein that the immune system learns to recognize. Here is where Bundibugyo diverges from the better-known Zaire strain: their glycoproteins are only about sixty percent identical. That genetic distance matters enormously. Two licensed vaccines already protect against Zaire Ebola. But limited pre-clinical studies suggest they offer little cross-protection against Bundibugyo. No one has tested this in humans—the gold standard—because the outbreak is happening now.
The real obstacle to a Bundibugyo vaccine is not the biology. Two working vaccines for Zaire prove the science is possible. The problem is money and incentive. Ebola affects relatively few people globally. Outbreaks are catastrophic, but they are also rare and localized. Pharmaceutical companies see no market. Vaccine development costs millions. The commercial return is negligible. Progress depends on governments, nonprofits, and organizations like the WHO. The other Ebola strains, which have caused larger outbreaks, got prioritized first.
Even when a vaccine is ready, the practical challenges multiply. The regions where outbreaks occur often lack robust healthcare infrastructure. Manufacturing, transport, storage, distribution—each step requires resources and speed. The existing Zaire vaccines work through viral vectors: scientists take a harmless virus, delete its disease-causing gene, insert the Ebola glycoprotein, and use that modified virus to train the immune system. Lambe's team uses a platform called ChAdOx, built from a chimpanzee adenovirus, which functions like a plug-and-play delivery system. It is elegant. It is proven. But it is only useful if it reaches people before transmission spreads beyond control.
Contact tracing—the backbone of outbreak response—is already failing. In regions with limited infrastructure and weak communication networks, finding everyone exposed to a confirmed case is nearly impossible. Vaccine skepticism compounds the problem. Lambe emphasized that honest communication matters: a vaccine's job is to keep people alive, not necessarily to prevent all symptoms or stop transmission entirely. During Covid, misconceptions flourished about what vaccines could do. The same will happen here unless scientists and public health officials speak plainly about limits and possibilities.
Why are Ebola outbreaks becoming more frequent in the twenty-first century? Climate change is reshaping where animals live and which viruses circulate. Humans are encroaching into habitats where these pathogens thrive. Globalization and mobility mean a localized outbreak can seed new regions. At the same time, diagnostic tools are improving. We can detect these viruses faster than we could before. Makinson noted that more strains may emerge. Bats carry viruses we have not yet identified. Scientists are surveying bat populations to understand what else is out there. The possibility is real. The work of building vaccines, of understanding ecology, of preparing infrastructure—it cannot stop with Bundibugyo.
Notable Quotes
We're behind on the outbreak response compared to where we've been in previous outbreaks. Initial testing on this outbreak was done on a different species of virus.— Rebecca Makinson, Oxford Vaccine Group
The main challenge is logistical and funding related. There's just not that normal market incentive that you'd get for pharmaceutical companies.— Rebecca Makinson, Oxford Vaccine Group
The Hearth Conversation Another angle on the story
Why did it take so long to identify that this was Bundibugyo and not another strain?
The initial testing was done on a different species of virus. By the time they figured out what they were actually dealing with, the outbreak had already gained momentum. That early identification window—when you can still contain things—was lost.
If we already have two working vaccines for Zaire Ebola, why can't we just use those?
The glycoproteins are only about sixty percent the same between the two strains. Pre-clinical studies suggest the existing vaccines don't offer much protection. We've never tested it in humans, but the genetic distance is too great to be confident.
What's the actual barrier to making a Bundibugyo vaccine quickly?
It's not the science. We know how to make Ebola vaccines. The barrier is that there's no money in it. Ebola affects relatively few people. Pharmaceutical companies won't invest without a market. So we depend on government funding and nonprofits, and those resources are always stretched thin.
You mentioned contact tracing is going to be difficult. Why?
In regions with limited healthcare infrastructure and weak communication networks, you can't reliably find everyone who was exposed to a confirmed case. If you can't trace contacts, you can't vaccinate them. And there's vaccine skepticism on top of that.
What's the most important thing people misunderstand about what a vaccine can do?
They think it will stop them from getting sick, or stop transmission entirely. The first goal is keeping people alive. If we can reduce symptoms, that's a bonus. But we need to be honest: a vaccine might not prevent infection. It might not stop you from feeling ill. It will try to keep you alive.
Are we going to see more Ebola strains emerge?
Almost certainly. We're warming the planet, encroaching into animal habitats, moving around more. Bats carry viruses we haven't even identified yet. Scientists are surveying them now, but there's a lot we don't know.