How the DRC’s Ebola Outbreak Could Devastate Gorilla Populations
by Samuel Peters
A new Ebola outbreak is spreading through the Democratic Republic of Congo. Scientists and conservationists are watching closely, because the last time Ebola arrived, it nearly wiped out its gorilla country.
On May 15, 2026, the Congolese Health Ministry confirmed a new outbreak of Ebola in the eastern Democratic Republic of Congo (DRC). The strain involved is Bundibugyo virus, one of six forms of Ebola virus within the Filoviridae family, and one for which there are no approved treatments or vaccines. The disease quickly spread into Uganda as more than 676 human cases were recorded and the death toll passed 136. The World Health Organization swiftly declared it a Public Health Emergency of International Concern (PHEIC).
As the human response mobilizes, a second alarm is sounding — quieter, but no less urgent — among the scientists, veterinarians, and park rangers who work to protect Africa’s great apes. The eastern DRC is home to some of the world’s most endangered gorilla populations. The overlap between the outbreak zone and gorilla habitat is not yet direct but it is close, and it is narrowing.
In 2002 and 2003, Ebola swept through the Lossi Gorilla Sanctuary in the Republic of Congo. Researchers monitoring the population watched as 91% of individually known gorillas in their study groups disappeared within a matter of months. Most were dead, as mortality rates ran high, up to 95%. Across a 5,000km2 study area, an estimated 5,000 western lowland gorillas perished. A subsequent 2004 outbreak in Odzala-Kokoua National Park extended the damage. In 2007, partly in response to the scale of those losses, the International Union for Conservation of Nature reclassified the western lowland gorilla as critically endangered: one category from extinction.
Researchers who studied the outbreaks described Ebola accurately as “a threat to the survival of African great apes.” That assessment has not changed. Today, all four gorilla subspecies sit at either endangered or critically endangered status. The western lowland gorilla is the most numerous, with about 316,000 remaining, the majority in the Republic of Congo. The other three subspecies exist in far smaller numbers and in far more precarious conditions.
Why Gorillas Are So Vulnerable
Gorillas live in close social groups, typically eight to ten animals gathered around a dominant silverback, with several adult females and their offspring. They spend hours each day in physical contact with each other: sleeping, grooming, and playing together. This closeness is central to their social structure and their wellbeing. It is also one of the primary reasons Ebola moves through gorilla groups so rapidly.
Damien Caillaud, a behavioral ecologist at the University of California, Davis, was in the field during the Lossi outbreak. He documented how the virus spread within groups through direct physical contact, particularly during rest and grooming. Nearly all gorillas in an affected group would disappear within a few weeks of the first death. Solitary males — those living apart from family groups — survived at far higher rates, which confirmed the link between social contact and transmission.
The behavior of gorillas around death compounds the risk. When a gorilla dies, the others do not simply move on. Healthy gorillas will stay near a dead body and will approach and touch the remains of individuals they encounter in the forest, even from other groups. Mothers have been observed carrying the bodies of dead infants for days, sometimes weeks. These responses are well-documented by scientists. But in the presence of Ebola, a carcass can remain infectious for several days, meaning that this behavior likely contributed to the spread of the virus across group boundaries during the early 2000s outbreaks.
Mountain gorillas are the subspecies under the most immediate threat from this outbreak. They live at the precise intersection of DRC, Uganda, and Rwanda: the same geographic corner where the current outbreak is concentrated. Their population has recovered significantly from a historic low of fewer than 300 in the 1980s and now stands at just over 1,000. It is one of the few genuine conservation success stories in great ape protection.
Dawn Zimmerman, a wildlife veterinarian at Yale University and the Smithsonian Institution, modelled what would happen if Ebola entered the mountain gorilla population through a single infected individual. Her findings, published in Scientific Reports in 2023, projected that fewer than 20 percent of the population would survive past 100 days post-infection. One case, introduced into a population of just over 1,000 animals, could effectively destroy decades of conservation effort.
The Grauer’s gorilla; the world’s largest nonhuman primate, also known as the Eastern lowland gorilla, lives exclusively in eastern DRC, the same region where the Ebola outbreak is now unfolding. Their population is estimated at fewer than 3,800, but that estimate is more than a decade old. Armed conflict across the region has made accurate monitoring impossible. Researchers require security escorts to reach field stations, and in some areas have been unable to work at all for months at a time. The honest answer is that nobody knows exactly how many Grauer’s gorillas remain, or where they all are.
Conservation is a Joint Effort
The response on the ground involves several organizations working together in often difficult and dangerous conditions.
Gorilla Doctors, an NGO providing veterinary care to wild mountain and Grauer’s gorillas, has teams on 24-hour call to investigate any suspected Ebola case in wildlife. Their chief veterinary and scientific officer, Tierra Smiley Evans, has described how parks have increased security at the boundaries of protected areas to limit the risk of infected people entering gorilla habitat. Rangers in both Virunga National Park and Kahuzi-Biega National Park have been trained to recognize the clinical signs of Ebola in great apes.
Emmanuel de Merode, director of Virunga National Park, has approximately 200 rangers positioned near gorilla populations. The park has established screening posts to check all travelers entering the area for signs of illness. Tourism, already suspended due to ongoing armed conflict in the region, has not resumed, removing one of the more common routes of disease transmission from humans to habituated gorilla groups.
The Dian Fossey Gorilla Fund is monitoring the situation across DRC and Rwanda and has teams actively preparing response protocols. The Fund has acknowledged that the outbreak is already placing strain on conservation operations more broadly, even in areas not directly affected.
Conservation work in this region has never been safe. In May 2026, two rangers were killed at a control post in Virunga National Park when an armed group opened fire. More than 200 rangers have lost their lives in the park since it was established in 1925. In this context, the local Congolese conservation body, Institut Congolais pour la Conservation de la Nature (ICCN), provides security escorts for researchers and works alongside international organizations on the ground to manage park security.
The Vaccine Question
One avenue that researchers have long advocated for, but which yet remains unrealized, is that of an Ebola vaccine for wild apes. Peter Walsh, a disease ecologist formerly at the University of Cambridge, developed an oral vaccine candidate that could be delivered through bait left in the forest, eliminating the need to tranquilize the animals. Laboratory results were encouraging as the immune response produced was comparable to that of an injected vaccine tested previously. The key practical advantage was significant: a single dose, delivered without human contact, across a large area.
The territories involved are vast and often remote. Distribution by field teams or drones has been proposed but never implemented at scale. Ethical frameworks governing research on great apes have complicated further testing. The result is that a tool which researchers believe could save thousands of animals exists only in a partially developed state, while the need for it grows more urgent with each new outbreak.
One factor which has received less attention than it deserves is the effect of U.S. funding cuts on the capacity for scientists and conservationists to respond to outbreaks. The Trump administration’s reduction of USAID and related international support programs has left a visible gap in conservation infrastructure across Central Africa. Many of the organizations monitoring gorilla populations and protecting their habitat were partially funded through these mechanisms. Staff have been cut, programs scaled back, and monitoring capacity reduced, precisely at the moment when the need for it is most acute. The United States was previously a leading contributor to Ebola outbreak response internationally. That infrastructure has contracted, and the consequences are now being felt both in the public health response and in the conservation operations that run alongside the current outbreak.
As of late June 2026, there are no confirmed or suspected cases of Ebola in any gorilla population. The outbreak zones and gorilla habitat have not yet directly overlapped. That distance is being actively maintained by the people described above, working under difficult conditions with reduced resources. How long it holds will depend on how effectively the human outbreak is contained, and on whether the barriers between infected areas and protected gorilla habitat remain intact.
Samuel Peters is an African ecologist and conservationist with the Wildlife Institute. He can be reached at samuelpete786@gmail.com