- In western Uganda, especially in districts bordering the Democratic Republic of Congo, human-bat interactions are frequent and can increase viral spillover risk, experts say.
- The Bundibugyo ebolavirus, a genetically distinct Ebola strain first identified in Uganda’s Bundibugyo district in 2007-2008, is driving the current outbreak.
- Experts warn that current Ebola vaccines and treatments, largely developed for the Zaire strain of ebolavirus, may offer limited protection against the Bundibugyo strain, underscoring major preparedness gaps.
- Field research highlights how humans may be exposed to these viruses including through hunting and consumption of bats in some communities, raising concerns about potential transmission of zoonotic pathogens.
KAMPALA — In the hills and trading centers of western Uganda, bordering the Democratic Republic of Congo, authorities are racing to limit the spread of Bundibugyo ebolavirus, a rare species of Ebola for which there is currently no vaccine or cure.
The number of suspected cases in the DRC is fast approaching 1,000, with Uganda reporting seven cases, as of May 25. The first cluster of cases of the ongoing outbreak was detected in early May in Ituri province in the DRC, which shares a border with Uganda. The close community and economic ties between people residing on both sides of the border has complicated efforts to contain the outbreak, with Uganda taking measures to stem the flow of people.
The Ebola virus driving the current outbreak is named for Uganda’s Bundibugyo district, where it was first detected almost two decades ago. (International health bodies including the World Health Organization have since moved away from naming disease-causing pathogens after places, citing stigmatization.)
Most Ebola outbreaks to date have been caused by the Zaire ebolavirus, which also drove the 2014-2016 epidemic centered on West Africa. The Bundibugyo ebolavirus has been linked to two outbreaks in the past. The second outbreak emerged in the DRC in 2012 remained limited to the country, before subsiding later that year.
This time may be different, since cases have emerged in Uganda, and the risk of regional spread is high. On May 23, the Africa Centres for Disease Control and Prevention (Africa CDC) identified 10 other African countries at risk from this Ebola outbreak: Angola, Burundi, the Central African Republic, the Republic of Congo, Ethiopia, Kenya, Rwanda, South Sudan, Tanzania and Zambia.
Bats are considered the most likely reservoir species for Ebola, including the Bundibugyo ebolavirus (Orthoebolavirus bundibugyoense), which is one of six species of the Ebola virus known to scientists.
In the border districts of western Uganda, bats are part of everyday life. They hang from fruit trees in household compounds, roost in ceilings above family homes, and fly through villages at dusk largely unnoticed.
Human interaction with bats is not associated with health risks among many residents, but scientists say these interactions can create conditions for spillover into human communities.
“The borders between Uganda and eastern DRC are extremely porous. People move freely, and diseases can move just as easily,” said James Natweta Baguma, a researcher affiliated with Makerere University School of Public Health in Kampala, the capital.
The Bundibugyo ebolavirus was first identified during an outbreak in Bundibugyo district in Uganda between 2007 and 2008. According to Pontiano Kaleebu, director of the Uganda Virus Research Institute, when the virus samples from the 2007 and 2008 outbreak were tested, the virus was identified as Ebola, but found to be genetically different from the Zaire and Sudan strains.
“It belongs to the same filovirus family, but it is slightly different,” Kaleebu said. “The disease presentation is largely the same, including the clinical picture and incubation period, but diagnostics require some differences because of genetic variation.”
Scientists say those genetic differences directly affect how outbreaks are diagnosed, treated and controlled.
Boghuma Titanji, assistant professor of medicine in the Division of Infectious Disease at Emory University School of Medicine in the U.S., said this variant differs genetically from the Zaire ebolavirus by roughly 32%.
“It’s most closely related to the Ebola virus isolated from Côte d’Ivoire, but it still diverges significantly from that species,” Titanji said.
That divergence is especially important because most existing Ebola vaccines and monoclonal antibody treatments were developed specifically for Zaire ebolavirus.
“Vaccines for Ebola Zaire and Ebola Sudan, which target the virus envelope glycoprotein, are unlikely to be effective [this time] because this protein target is so different for Bundibugyo ebolavirus,” Titanji said. “The same goes for monoclonal antibodies developed for treatment of individuals with Zaire virus.”
The viral glycoprotein is central to how vaccines and antibody therapies recognize and neutralize the virus. But because Bundibugyo’s glycoprotein differs substantially from the Zaire strain, scientists still do not know whether current vaccines would offer meaningful protection.
“We do not know whether the immune response generated by Zaire virus vaccines will be sufficiently cross-reactive to offer meaningful protection against Bundibugyo ebolavirus,” Titanji said.
She noted that answering this question would require studies during an active outbreak, a process often constrained by emergency priorities such as contact tracing, containment, and treatment setup.
Kaleebu said the Bundibugyo strain can still be identified rapidly once samples reach laboratories, often within four hours using appropriate diagnostic tools.
“If you have the right test, you can detect it like any other Ebola virus,” he said.
However, scientists warn that preparedness gaps surrounding Bundibugyo ebolavirus have existed for years.
“We have known about the existence of this virus and its ability to cause outbreaks for almost two decades,” Titanji said. “Yet market incentives did not exist for this to translate into vaccines and therapeutics.”
She added that reductions in international health funding have further strained surveillance systems in parts of Africa that rely heavily on external support for outbreak logistics and operations.
Scientists still do not fully understand where Ebola viruses persist in nature. Although bats are widely considered the most likely reservoirs, researchers caution that the precise way it survives and circulates in nature — including its natural host, how it moves between animals, and how it is transmitted to humans — remains unclear.
“The biggest unknown is where these viruses hide and in which animals,” Kaleebu said. “Many people say bats, but there is still no conclusive proof.”
“There are more than 1,000 bat species globally, and several are common in western Uganda,” said Baguma, the public health researcher.
Even so, field observations in western Uganda show frequent and sustained human contact with bats.
“In Bundibugyo, bats are everywhere — in people’s houses, compounds, and trees,” Baguma said. “For many communities, living closely with bats is considered normal.”
The researchers also found that bats are a part of the local diet. “People hunt and eat bats because they are an accessible source of protein,” Baguma said. “For many households, it is easier to catch bats than to buy beef or goat meat.”
He said some members of the Indigenous Batwa community maintain forest-based hunting and food practices reflecting long-standing cultural and livelihood ties to the forest. There is a painful legacy of government efforts to resettle communities, sometimes forcibly, which has eroded the trust required to work with forest-dependent peoples.
“Some still go into forest areas to hunt bats, monkeys, and other wildlife,” Baguma said.
Scientists say these interactions create multiple pathways for potential spillover, including direct handling of bats, consumption of bat meat, contact with bat saliva on fruit, and bats roosting inside homes.
Communities in the region distinguish between larger fruit bats, often seen feeding in trees and more commonly eaten, and smaller insect-eating bats, which roost in ceilings and are usually avoided due to smell and droppings.
Beyond daily exposure, cultural beliefs also shape risk. “Some people believe eating bat meat improves sexual performance or brings wealth,” Baguma said. “Others believe that having bats in the house is a sign of prosperity.”
At the same time, some beliefs discourage contact, including the view that pregnant women should avoid bat meat. “These beliefs work both ways,” Baguma said. “Some increase risk, while others may reduce interaction.”
Public health experts say one of the biggest challenges is perception. Many residents do not believe bats pose danger because they have lived alongside them for generations without visible illness.
“Some people tell you, ‘If bats carried diseases, we would already be dead,’” Baguma said.
That perception worries scientists, particularly as Ebola outbreaks continue across the region. Uganda last experienced a major Sudan Ebola outbreak in 2022, while the DRC continues to report periodic flare-ups.
According to researchers, outbreak response often begins only after infections are confirmed, while long-term prevention in high-risk communities remains inconsistent.
Baguma said that in some high-risk areas, prevention measures are not consistently observed, describing the situation as “almost living on God’s grace,” and noting that the observed behaviors do not reflect strong efforts to prevent outbreaks.
For Titanji, Bundibugyo ebolavirus underscores broader gaps in preparedness that have persisted since its discovery nearly two decades ago.
“A truly species-specific preparedness strategy would require vaccines and therapeutics targeted to the known Ebola viruses,” she said.
She warned that emerging pathogens continue to expose a structural weakness in global health systems.
“We will always be caught short-handed,” Titanji said, “unless there is greater investment in early detection systems capable of identifying these threats before they grow.”
For now, scientists say prevention remains the strongest defense: rapid detection, community awareness, reduced wildlife contact, and stronger surveillance in regions where humans and wildlife continue to interact closely.
“We still need stronger public education through radio, television, and community outreach,” Baguma said. “People need to understand that these risks are real before the next outbreak begins.”
Banner image: The nonprofit ASD Monde is providing handwashing kits to schools in Nyiragongo territory, North Kivu province, in the eastern DRC. Image courtesy of ASD Monde.
Citations:
Baguma, J. N., Namusisi, S., Ninsiima, L. R., Musiitwa, R., Tamale, B. N., Amperiize, M., … Kato, C. D. (2025). Bat-human interactions and associated factors among communities in Bundibugyo district, Uganda: A cross-sectional study. PLOS Global Public Health, 5(8), e0004249. doi:10.1371/journal.pgph.0004249
Towner, J. S., Sealy, T. K., Khristova, M. L., Albariño, C. G., Conlan, S., Reeder, S. A., … Nichol, S. T. (2008). Newly discovered Ebola virus associated with hemorrhagic fever outbreak in Uganda. PLOS Pathogens, 4(11), e1000212. doi:10.1371/journal.ppat.1000212
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