A new Bundibugyo virus outbreak in the Democratic Republic of Congo has brought attention back to one of the lesser-known species in the ebolavirus family. The World Health Organization has reiterated that the risk of international spread remains low for the general population. For the scientific community, though, this virus is a genuine test case: developing vaccines and therapies becomes far harder when an infectious agent appears rarely and produces only a limited number of cases.
According to the ECDC, as of 19 July 2026 (data updated to 18 July), the Democratic Republic of Congo had recorded 2,344 confirmed cases and 930 deaths, with 724 patients currently hospitalised in isolation. The previous 24 hours had added 83 new confirmed cases. Of the patients who tested positive for Bundibugyo virus, 466 have recovered, and 85.8% of identified contacts are under active surveillance in the provinces of Ituri, North Kivu and Tshopo.
The story of Bundibugyo virus helps explain how research investment in emerging infectious diseases gets prioritised, and why some viruses have dedicated vaccines and therapies while others still have none.
Ebola virus disease is often talked about as if it were a single pathogen. In reality, several species of ebolavirus can cause it, sharing some traits but differing in significant biological ways. That distinction explains why results obtained against one species don't automatically transfer to another.
«Most of the scientific investment of the past twenty years has focused on Zaire ebolavirus, responsible for the most devastating outbreaks, including the 2014-2016 West Africa epidemic, which caused more than 28,000 cases and over 11,000 deaths» says Antonella Castagna, Full Professor of Infectious Diseases at Vita-Salute San Raffaele University.
Zaire ebolavirus, in fact, is the species against which today's approved vaccines and monoclonal antibodies were developed. The high case numbers recorded during its outbreaks made it possible to collect the clinical data, biological samples and information needed to launch experimental studies and clinical trials. The situation looks very different for Bundibugyo virus.
A good scientific idea isn't enough to develop a vaccine. Researchers need biological samples, systematically collected clinical data, immunological studies and, where possible, trials conducted during active outbreaks. When a virus causes few epidemics and affects a limited number of patients, building this body of knowledge inevitably takes longer.
«The Bundibugyo ebola virus (BDBV) is rare compared with other ebolaviruses. Before the current outbreak, only a few significant outbreaks had been documented: the first in Uganda in 2007, with around 149 cases, and a second in the Democratic Republic of Congo in 2012, with around 57 cases. Altogether, we're talking about a few hundred cases over nearly twenty years. Bundibugyo also tends to have lower lethality than Zaire ebola virus: while the latter can reach fatality rates of 60-90% without adequate treatment, available data for Bundibugyo point to a lethality of around 30-50%» she explains.
How often these viruses emerge has directly shaped international research priorities. Focusing on Zaire ebola virus delivered important results, but it left the question of other ebolavirus species open, and equally effective tools still don't exist for them today.
«The monoclonal antibodies currently approved against Ebola, developed against Zaire ebola virus, don't necessarily guarantee the same efficacy against Bundibugyo, because the different viral species behave differently» Castagna notes.
Research is working to overcome this limitation. What's needed are strategies that protect against different viruses at once, rather than developing a separate vaccine for each Ebola virus species. «The real challenge today is moving from a “virus by virus” approach to vaccine and therapeutic platforms able to protect against multiple ebolavirus species at once».
Ebola outbreaks over the past twenty years have profoundly changed how new cases are detected and monitored. In the past, weeks or even months could pass before the responsible virus was precisely identified. Today, the availability of more advanced diagnostic technologies and international collaboration networks allows a much faster response.
«This outbreak shows that modern epidemiological surveillance isn't just about reporting cases. It's about building a network capable of reacting quickly» Castagna says. «Uganda and the Democratic Republic of Congo are extremely complex settings: the affected areas combine security problems, constant cross-border movement, food crises and limited access to health services. The most important lesson is that speed makes the difference».
Genomic sequencing has become one of the most important tools in outbreak response over the past few years. Rapidly identifying a virus's genetic makeup confirms diagnoses, tracks how an outbreak evolves, and allows information to reach international research centres quickly.
«Today we can genetically identify a virus within days, thanks to sequencing technologies that weren't available in the field during the early Ebola epidemic», Castagna points out. «We can also share genomic data almost in real time between African, European and American laboratories».
As our article on Andes virus also explains, the experience gained during the COVID-19 pandemic helped accelerate this process. Many countries strengthened their laboratory networks, expanded molecular diagnostics and consolidated collaboration procedures that now prove valuable for tackling other emerging infectious diseases.
How effectively an epidemic response works doesn't depend on diagnostic tools alone. Local community cooperation remains one of the most delicate elements, especially when isolation or contact-tracing measures clash with established cultural practices or fuel distrust of health institutions.
«That's why we increasingly talk about a “community-centred” approach», Castagna observes. «Involving local leaders, community health workers and civil society organisations from the earliest stages of the response can make a real difference».
On 13 July 2026, the WHO declared the outbreak a Public Health Emergency of International Concern (PHEIC), the third such declaration for Ebola in the region since 2019. On 17 July, WHO Director-General Tedros Adhanom Ghebreyesus stated that this is the third-largest Ebola epidemic ever recorded, spreading faster than any previous one. The outbreak in Uganda, however, appears to be over: the last patient has been discharged after recovering, and the country will be able to declare the outbreak closed after 42 days without new infections.
«The WHO's risk assessments are based on models that combine epidemiological, biological and logistical data», Castagna explains. «In the case of Bundibugyo virus, the global risk is considered very low for several reasons. First, Ebola isn't an airborne virus like SARS-CoV-2: transmission requires direct contact with the blood, secretions or other bodily fluids of symptomatic or deceased people. That makes international spread far less “efficient”».
The new joint plan launched by the WHO and Africa CDC does more than fund the response to the current outbreak. Its goal is to build lasting capacity in health systems to face future emergencies.
«I believe this plan represents one of the most important cultural shifts in modern public health», Castagna comments. «The funding planned for June-November 2026 goes beyond managing the emergency: it funds structurally strengthening health systems. The areas of investment include laboratories, surveillance, staff training, infection prevention, logistics, community engagement and clinical research. This is what we mean by preparedness, as opposed to reacting once an emergency is already underway».
According to Castagna, the concept of preparedness should play an increasingly central role in university training too. «From a training perspective, I believe Italy also needs to invest more in preparedness. It's important to educate professionals who can manage the diagnostic and treatment pathway, but who are also prepared on the epidemiological side: managing health data, communicating risk and conducting clinical research in emergencies. Investing in preparation costs far less than managing a crisis once it's already out of control» Antonella Castagna concludes.