- Gorillas are vulnerable to communicable diseases that infect humans and other non-human primates, including the Ebola virus.
- A new Ebola outbreak was announced in the Democratic Republic of Congo in mid-May, but so far, there have been no reported cases of gorilla infection. Previous outbreaks have devastated western lowland gorillas.
- Armed conflict hampers both conservation and efforts to monitor both Grauer’s and mountain gorilla populations in DRC. They also impair the public health response, which has also been seriously impacted by cuts in U.S. funding under the Trump administration.
- Gorillas are highly social animals, which facilitates spread of infectious disease. Infants and females are disproportionately affected, which has serious consequences for recovery of devastated populations.
As human cases continue to climb in the latest outbreak of the deadly Ebola virus in the Democratic Republic of the Congo, concern is growing for the gorilla population, which have been devastated by the virus during previous outbreaks.
On May 15, the Congolese Health Ministry announced a new outbreak of the lethal virus, which has struck the country at least 17 times over the past half-century; the World Health Organization (WHO) declared it a Public Health Emergency of International Concern.
The U.S. Centers for Disease Control and Prevention confirmed 676 Ebola cases in the eastern DRC and 136 deaths as of June 10 — and continue to rise. In neighboring Uganda, 19 cases and two deaths have been reported, with no new cases in the last days. So far, the outbreak seems to be largely contained within the region.
The Bundibugyo virus is the culprit, one of five Ebola viruses within the family Filoviridae that spark illness in people. It has no approved treatment or vaccine.
As cases mount, virologists — as well as ecologists and primatologists — are warily monitoring its spread. First discovered in humans in 1976 along the Ebola River (where it got its name), Ebola is highly contagious, and this virus can also sicken and kill gorillas and other non-human primates. While some symptoms are flu-like — fever, vomiting and diarrhea — the disease can progress to a gruesome, often-fatal hemorrhagic fever, causing both internal and external bleeding.
Previous outbreaks have exacted vast human death tolls — but they’ve also decimated non-human primate populations in Central Africa. Researchers have called Ebola “a threat to the survival of African great apes.”
While there is currently no overlap between areas with reported cases and gorilla habitat in Uganda and DRC, the situation is evolving rapidly.
If it was to spread into areas populated by any of the four critically endangered gorilla subspecies, the consequences could be catastrophic.
A heavy toll on gorillas
Ebola is zoonotic, a type of disease that’s capable of jumping between livestock, wildlife and humans. Ebola is transmitted through direct contact with infected blood or body fluids — and by eating infected animals: bushmeat. Researchers have called the hunt for the virus’s natural host to be “an enduring mystery.” Testing from 1979-2025 found Ebola infection in 61 mammal species out of some 360 that were tested.
Western lowland gorillas (Gorilla gorilla gorilla) in the Republic of Congo have suffered massive losses during back-to-back human outbreaks, one near the Lossi Gorilla Sanctuary in 2002–2003 and another in Odzala-Kokoua National Park in 2004. With mortality rates from 90-95%, about 5,000 western lowland gorillas died in Lossi, a 5,000 square kilometer (1,930 square mile) study area, according to a report in the journal Science.
In concert with habitat loss and illegal hunting, the IUCN, the global wildlife conservation authority, changed its conservation status to critically endangered in 2007, one step from extinction. As of the last IUCN assessment, published in 2018, about 316,000 remained, with 60% in the Republic of Congo.
The other three subspecies seem to have been unaffected thus far. “As far as we know, all past Ebola outbreaks that have affected gorillas concerned the western lowland gorilla,” said Damien Caillaud, a behavioral ecologist at the University of California, Davis, in the U.S.
Gorillas’ close relationships can prove deadly
Gorillas are at great risk from infectious disease, because they’re social animals. They typically live in groups of eight to 10, typically a single adult male, several adult females and their offspring. Some adult males are solitary, waiting to find or form a group.
Caillaud witnessed firsthand the devastation of the early 2000s Ebola outbreak. He co-authored a paper on how gorilla sociability and group dynamics affect exposure.
“During these outbreaks,” he said, “we observed that Ebola spreads rapidly within gorilla groups, likely due to the physical contacts gorillas have during nap time, play or grooming sessions.” They found that solitary males are much less susceptible, but female gorillas are disproportionately affected, which makes it difficult for the population to recover.
When one animal is affected, transmission is fast. “Almost all the gorillas from the group disappear within a few weeks,” he said.
The researchers in Lossi observed the same level of mortality. They reported that “from October 2002 to January 2003, 91% (130/143) of the individually known gorillas in our study groups had disappeared.”
Gorillas stay near the dead body of a recently deceased individual, regardless of whether it belonged to their social group, according to a report in the journal Zoological Science. The researchers observed that healthy gorillas “will likely touch the body of a gorilla they randomly bump into in the forest,” Caillaud said.
Infant “corpse-carrying” behavior has also been observed in gorillas, where a mother carries an infant’s body for days — or even weeks — after its death, Tierra Smiley Evans, chief veterinary and scientific officer with the NGO Gorilla Doctors wrote in an email to Mongabay.
When gorillas die from Ebola, their dead bodies remain infectious for several days. It’s why carcasses “likely constitute one of the main sources of infection for unaffected gorilla groups ranging nearby,” Caillaud said. This could be one of the main pathways of infection that killed thousands of individuals in the early 2000s, he added.
But in general, these are very social beings. “We generally say that gorillas are not good at social distancing within their family group, but [different] gorilla families don’t come into contact with each other on a daily basis … so that can help limit spread across a population,” said Tara Stoinski, CEO of the Dian Fossey Gorilla Fund.
Guerillas in their midst
Every one of the four gorilla subspecies are in trouble, either endangered or critically endangered. There are two distinct species, Eastern (Gorilla beringei) and Western (Gorilla gorilla), each with two subspecies.
As of the 2018 IUCN assessment, just over 1,000 Eastern mountain gorillas (G.b. beringei) were left in the wild in Virunga National Park and Bwindi Impenetrable National Park. Mathematical modeling from a 2023 study suggests that if just one contracted Ebola, it could “decimate the population,” with “less than 20% projected to survive at 100 days post-infection.”
There are even fewer Cross River gorillas (G. g. diehli). An accurate estimate is difficult because they’re elusive and correspondingly difficult to monitor. The nonprofit Wildlife Conservation Society numbers them at under 300 individuals that live in small, fragmented habitat along the Cameroon-Nigeria border. With so few remaining, “any infectious agent” could devastate this delicate population, according to the Cross River Gorilla Alliance.
Population figures for the critically endangered Grauer’s gorilla (G.b. graueri), also known as the Eastern lowland gorilla, are a matter of conjecture: Armed conflict and ethnic violence have prevented accurate accounting in their only home, the eastern DRC, and researchers need official government security teams to work there. A report in 2016 documented the collapse of Grauer’s gorillas — the world’s largest non-human primate — over the previous two decades. Their numbers have plummeted by 77%, from 16,900 to fewer than 3,800. But that estimate is now a decade old.
“For months before [this current] outbreak began, we had not been able to monitor the Grauer’s gorillas in Kahuzi-Biega National Park in DR Congo because of insecurity,” Evans with Gorilla Doctors said. “Our teams also have to be escorted by ICCN [Institut Congolais pour la Conservation de la Nature, a local NGO] for any travel to and from field stations in Virunga National Park.”
Government workers, in concert with conservation groups, are working to minimize the risk of Ebola virus transmission to gorillas and park personnel; monitoring the spread of the human outbreak in relation to gorilla habitat; and providing protective equipment and sanitization facilities.
As part of that effort, Evans said, parks have increased security along protected area boundaries to reduce the risk of infected people entering illegally and placing gorillas at risk. Rangers have also received training to recognize the clinical signs of Ebola in gorillas.
Ebola experts have previously voiced concern that mistrust of health authorities during Ebola outbreaks could raise the risk of infected people hiding in areas populated by non-human primates.
Protecting these gorillas is dangerous — and all too often deadly — work. In May 2026, two rangers were killed at a control post in DRC’s Virunga National Park when an “unidentified, heavily armed group” opened fire. More than 200 rangers have died in the line of duty since the park was established in 1925.
Ebola response in 2026
The loss of funding and resources from the United States is having a profound impact on the ability to control the current human outbreak. The U.S. was a leading force in Ebola and other infectious disease response until President Donald Trump drastically cut funding to USAID and other agencies.
What may be less well known, Evans said, is how the loss of U.S. international support has also impacted conservation organizations.
“Many conservation groups that were funded by USAID and other U.S. international support mechanisms have had to scale back staff and cut programs, and this has impacted wildlife monitoring and habitat protection,” she said.
To date, there are no reported or suspected cases of the Bundibugyo strain in any gorilla population. If there is a suspected case or reports of a suspected case in a monkey, bushbuck, duiker, bush pig, porcupine or other species, the Gorilla Doctors team is on call 24/7 to investigate alongside park authorities.
Caillaud said mountain gorillas are found in Rwanda, DRC and Uganda, “pretty close” to the current outbreak. If Ebola infects gorillas this time, its spread will depend on the overall gorilla density, which is low in eastern DRC where Ebola has broken out this time, he said. Caillaud added that the western lowland gorillas that perished in such large numbers 20 years ago lived in much tighter proximity.
At low densities, he said, the risk of a large outbreak affecting eastern gorillas in DRC is “quite limited.”
However, vigilance remains the order of the day: As the 2023 study showed, all it takes is one case.
Banner image: Just over 1,000 mountain gorillas remained in DRC’s Virunga National Park and Bwindi Impenetrable National Park as of 2018. If just one of them contracted Ebola, it could “decimate the population,” with less than 20% projected to survive at 100 days post-infection. Image by Cai Tjeenk Willink via Wikimedia Commons (CC BY-SA 3.0).
Gunmen kill two rangers in latest deadly attack in DRC’s Virunga National Park
The environmental toll of the M23 conflict in eastern DRC (Analysis)
Proposed Trump policy threatens Critically Endangered Grauer’s gorilla
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