EBOLA RETURNS — AND THIS TIME WE HAVE NO VACCINE
The 2026 Bundibugyo outbreak, a WHO emergency, and the dangerous gap in our preparedness
Since its discovery in 1976, Ebola virus has caused more than 40 confirmed outbreaks across sub-Saharan Africa, sixteen of them in the Democratic Republic of Congo (DRC). Health systems in the region have developed protocols, trained responders, and, since 2019, relied on a licensed vaccine to reduce transmission among those most at risk. That vaccine, rVSV-ZEBOV (Ervebo), has been a critical tool. It works against the Zaire strain, which has driven virtually every major DRC outbreak. But the 2026 outbreak is different.
On 15 May 2026, the DRC Ministry of Health declared an Ebola outbreak in Ituri Province in the north-eastern part of the country. The causative agent is Bundibugyo virus (BDBV), a rare Ebola species for which there is no approved vaccine and no approved treatment. Within 24 hours, cases had crossed the border into Uganda. Within 48 hours, a confirmed case was identified in Kinshasa, the DRC’s capital, some 1,700 kilometres from the epicentre. On 17 May 2026, the World Health Organisation (WHO) declared the outbreak a Public Health Emergency of International Concern (PHEIC).
As of 16 May, there were 246 suspected cases and 80 suspected deaths across at least three health zones in Ituri, alongside three laboratory-confirmed cases in Uganda and Kinshasa. These numbers almost certainly understate the true incidence. A high positivity rate in initial testing, eight confirmed positives from just thirteen samples, points to a much larger undetected outbreak.
What is Bundibugyo virus?
The genus Orthoebolavirus contains six recognised species. Four are known to cause disease in humans: Zaire, Sudan, Tai Forest, and Bundibugyo. Zaire has been responsible for the most catastrophic outbreaks, including the 2013–2016 West African epidemic that infected nearly 30,000 people and killed over 11,000. Sudan has caused nine outbreaks since 1976, most recently in Uganda in January 2025. Tai Forest has infected only a single confirmed human case, in 1994.
Bundibugyo virus was first characterised as a distinct species in 2007–2008, when an outbreak struck Bundibugyo District in western Uganda, a region that borders the DRC. That outbreak produced 131 reported cases and 42 deaths. A second outbreak occurred in 2012, in Province Orientale in the DRC, resulting in 38 laboratory-confirmed cases and 13 deaths. Molecular analysis of the 2012 outbreak suggested the possibility of multiple independent spillover events from an animal reservoir, rather than a single introduction with subsequent human-to-human spread.
The 2026 outbreak is therefore only the third documented Bundibugyo event in human history and, by a considerable margin, the largest. It has already surpassed both previous outbreaks combined in suspected case count, and has demonstrated rapid cross-border spread within weeks of its presumed index case.
In clinical presentation, Bundibugyo infection closely resembles Ebola Zaire. Onset is typically sudden, with fever, fatigue, muscle pain, headache, and sore throat - flu-like symptoms - in the early phase, progressing to vomiting, diarrhoea, rash, and haemorrhagic features - internal and external bleeding - in severe disease. The incubation period runs from 2 to 21 days, averaging 8–10 days. One notable difference: the case fatality rate (CFR) for Bundibugyo is estimated at 30–40%, somewhat lower than the 70–90% seen in untreated Zaire outbreaks.
The diagnostic blind spot: how the outbreak grew unseen
A notable feature of this outbreak is how long the virus spread before anyone knew what it was. The earliest known case is a nurse who developed symptoms on 24 April 2026 and died at the Evangelical Medical Centre in Bunia, Ituri’s provincial capital. Yet the outbreak was not declared until 15 May - three weeks later.
The reason lies in a critical diagnostic gap. Field testing for Ebola in the DRC relies heavily on the GeneXpert platform, which is designed to detect Ebola Zaire, the strain responsible for almost all previous DRC outbreaks. When samples from the affected health zones were tested in Bunia, they returned negative. It was only when samples were sent to the National Institute of Biomedical Research (INRB) in Kinshasa, where multi-species Ebola assays are available, that the Bundibugyo strain was identified.
Decades of Zaire-centric outbreaks have shaped surveillance infrastructure, diagnostic capacity, and response protocols around a single viral species. When a different species arrives, with identical clinical features but a different genome, diagnosis can be missed. The result is unchecked community transmission during the period when containment is most achievable.
The head of epidemiology and global health at INRB, Placide Mbala, has been explicit: a rapid field-deployable test capable of detecting Bundibugyo virus is urgently needed. This is an immediate requirement for which no solution is currently available.
Why containment is especially difficult
Ebola outbreaks are always hard to contain. This one more so.
Firstly, there is no vaccine. The rVSV-ZEBOV vaccine, deployed with considerable success in the 2018–2020 DRC outbreak, is specific to Ebola Zaire. It offers no protection against Bundibugyo virus. A ring vaccination strategy, the primary tool that helped control the last major DRC outbreak, is simply not available here. The absence of both vaccine and licensed drug therapy means the entire response burden falls on isolation, contact tracing, infection prevention and control (IPC), and safe burial practices.
Ring vaccination, sometimes called reactive or targeted vaccination, is a strategy in which, rather than vaccinating entire populations, you rapidly identify and vaccinate the social and geographic ‘ring’ of people most at risk around each confirmed case: household contacts, close community contacts, and the healthcare workers who treated them. The logic is to build a protective barrier around the virus before it can reach the wider population, cutting off transmission chains at source.
This strategy, deployed with rVSV-ZEBOV, proved effective during the 2018–2020 North Kivu and Ituri epidemic, which, despite lasting nearly two years in a conflict zone, was ultimately contained without becoming a global catastrophe. By the end of that outbreak, more than 303,000 doses had been administered. Clinical evidence from Guinea’s 2015 Ebola Ça Suffit! trial demonstrated that rVSV-ZEBOV achieved approximately 100% efficacy in vaccinated contacts, giving responders a genuinely powerful and precisely targeted tool.
None of that is available now. With no licensed vaccine for Bundibugyo virus, outbreak control reverts entirely to the pre-vaccine toolkit: early detection, isolation of cases, exhaustive contact tracing, rigorous infection prevention and control (IPC) in health facilities, and safe and dignified burial practices to prevent transmission from deceased individuals. Each of these interventions is demanding under ideal circumstances; in a conflict-affected, resource-constrained setting with a three-week diagnostic delay already embedded, the challenge is huge.
Secondly, the outbreak is occurring in a highly insecure environment. Ituri Province has been the scene of sustained inter-communal violence and militia activity for years. Armed groups, including those affiliated with the Islamic State, operate in and around the affected health zones.
This directly impedes response efforts: it restricts the movement of health workers, disrupts community engagement, damages trust in health authorities, and can render entire areas inaccessible. The 2018–2020 DRC Ebola outbreak in North Kivu and Ituri - also complicated by conflict - ultimately lasted nearly two years and became the second-largest Ebola outbreak in history.
Thirdly, population mobility in the region is high. Ituri shares porous borders with Uganda and South Sudan. Mining activity in Mongwalu creates significant cross-border movement of workers. Urban centres such as Bunia serve as transit hubs. These are precisely the conditions under which outbreaks amplify geographically. Confirmed cases in Kampala, Uganda’s capital, and in Kinshasa demonstrate that the virus is already using established mobility networks to spread.
Fourth, healthcare-associated transmission appears to be occurring. At least four of the eight laboratory-confirmed cases in DRC are healthcare workers, suggesting nosocomial spread. At least four healthcare worker deaths compatible with viral haemorrhagic fever have been reported from affected areas. This pattern, seen repeatedly in Ebola outbreaks, reflects the extreme IPC demands of managing viral haemorrhagic fever patients and the catastrophic consequences of inadequate protective equipment or training.
The WHO declaration and the global response
On 17 May 2026, WHO Director-General Tedros Adhanom Ghebreyesus declared the outbreak a Public Health Emergency of International Concern under the International Health Regulations (2005). The PHEIC designation, the WHO’s highest alert level, indicates that the event is extraordinary, constitutes a public health risk through international spread, and requires coordinated global action.
WHO explicitly noted that the outbreak does not meet the criteria for a ‘pandemic emergency’ but that countries sharing land borders with the DRC are at high risk of further spread. States have been advised to activate national emergency management mechanisms, strengthen cross-border surveillance, implement screening at major transit points, and prepare health facility IPC capacity.
Africa CDC convened an urgent high-level regional coordination meeting on 15–16 May, bringing together health authorities from DRC, Uganda, and South Sudan alongside WHO, UNICEF, Médecins Sans Frontières (MSF), the Gates Foundation, the Wellcome Trust, pharmaceutical partners including Gilead Sciences, Merck, Regeneron, BioNTech, and Moderna, and multilateral funders including the World Bank and the African Development Bank. MSF has announced preparations for a large-scale operational response in Ituri.
The involvement of vaccine and therapeutics manufacturers at this early stage reflects both the urgency of the situation and the current void: no approved product exists for Bundibugyo virus, and there is the question of how rapidly candidate interventions might be evaluated and deployed.
An outbreak that was always going to hit hardest here
The communities bearing the burden of this outbreak, in one of the world’s poorest and most conflict-affected regions, have been rendered vulnerable by forces that long predate this virus. Decades of extractive colonialism, post-independence political instability, and ongoing conflict over the region’s mineral wealth have left Ituri’s health infrastructure chronically underfunded and repeatedly disrupted.
The informal health facilities and gaps in IPC capacity that WHO identifies as outbreak amplifiers are not accidents; they are the product of sustained underinvestment and institutional neglect.
The diagnostic blind spot described above, Zaire-centric surveillance infrastructure failing to detect a different species, is also, in part, a resource allocation story. Comprehensive multi-species diagnostic capacity requires sustained funding that has not been consistently available. The same applies to research pipelines for Bundibugyo-specific vaccines and therapeutics; because previous Bundibugyo outbreaks were small and geographically contained, they generated insufficient commercial interest to drive product development.
It is also worth noting the timing. The outbreak is unfolding against the backdrop of significant reductions in global health funding, including cuts to USAID programming, which have reduced both surveillance capacity and community health infrastructure across Central and East Africa. A global health security architecture already under financial strain is being tested at a time when the potential consequences are most severe.
What does this mean for the UK?
The direct risk to the UK from this outbreak, based on current evidence, remains low. Ebola is not airborne. It spreads through direct contact with the bodily fluids of symptomatic individuals. There is no documented sustained transmission of any Ebola species outside Africa; even during the 2013–2016 West African epidemic only a handful of cases were exported to Europe, almost all among repatriated healthcare workers.
The UK Health Security Agency (UKHSA) maintains standing protocols for viral haemorrhagic fever (VHF) in returning travellers. NHS England High Consequence Infectious Disease (HCID) units — currently designated at Royal Free London, Royal Victoria Infirmary Newcastle, and Sheffield Teaching Hospitals — are equipped and staffed to manage suspected Ebola cases under negative-pressure isolation with full barrier precautions.
However, the absence of a Bundibugyo-specific vaccine or antiviral introduces an additional dimension of clinical uncertainty. In the event of an imported case, the two licensed Ebola therapeutics, atoltivimab/maftivimab/odesivimab (Inmazeb) and ansuvimab (Ebanga) - monoclonal antibodies which target Ebola Zaire glycoprotein used to gain access to target cells, are unlikely to be effective against Bundibugyo virus. Treatment would necessarily be supportive, as in the affected DRC communities. Clinicians should be aware of this in the unlikely event that a returning traveller from eastern DRC or Uganda presents with a febrile illness and relevant exposure history.
The probability of such an event remains very low. Nonetheless, this outbreak is a reminder that the UK’s imported VHF preparedness must account not only for the most common Ebola strain, but for the full range of viral haemorrhagic fever pathogens - a lesson that was underlined, but not fully implemented, after previous Sudan virus and Marburg alerts.
Conclusion
The 2026 Bundibugyo Ebola outbreak in the DRC is the most significant Ebola event since the 2018–2020 North Kivu epidemic. It is the first WHO PHEIC for Ebola in six years, the largest documented Bundibugyo outbreak on record, and the first to demonstrate rapid multi-country spread within days of its identification. The outbreak exposes critical gaps: diagnostic infrastructure calibrated for a single strain, a vaccine availability that does not cover rare Ebola species, and a global response system under growing resource pressure.
The communities at the centre of this outbreak are once again facing the severest consequences. The international response, now formalised under PHEIC, must be sustained, well-resourced, and attentive to the structural conditions that made this crisis possible. For the global health community, this outbreak is both a test and a reckoning.
References
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