In a cave in Africa, cameras captured wild animals periodically hunting bats or eating carcasses. The prey was the Egyptian fruit bat, the host of the Marburg virus that causes deadly hemorrhagic fever. Humans may have triggered the fuse of a deadly infectious disease. A tourist who visited this place in the past died of Marburg, and over roughly a year of research, cameras also captured hundreds of people.
Alexander Braczkowski of the Uganda Kambura Lion Project and colleagues said, "In Python Cave in Uganda, where Egyptian fruit bats live, we used motion-triggered cameras over 368 days to record 321 events in which 14 species of wild animals came into contact with bats," in the international journal Current Biology on Mar. 20 (local time).
◇ First images of a leopard hunting bats
If infected with the Marburg virus through an infected person's blood or bodily fluids, people experience chills, headaches, vomiting and diarrhea, and after about a week, bleeding occurs. The fatality rate exceeds 25%. The Marburg virus belongs to the Filoviridae family along with the virus that causes Ebola hemorrhagic fever, whose fatality rate exceeds 75%. Both have the Egyptian fruit bat as a host, and it is presumed that people become infected via wild animals that serve as intermediate hosts.
Last year, the researchers installed motion-triggered camera traps that automatically take photos when animals pass by to observe African leopards and spotted hyenas in Queen Elizabeth National Park in western Uganda. Contrary to expectations, the cameras captured numerous wild animals going in and out of a cave in front of them. The team said this is the first time wild animals that could be intermediate hosts of the Marburg virus have been clearly filmed.
Video shows a variety of animals—including leopards, hyenas, eagles, monitor lizards and monkeys—catching bats in the cave or biting and eating them. A leopard carrying a bat in its mouth was filmed 43 times. This is the first confirmation that leopards hunt bats. They even captured scenes of a crowned eagle and a Nile monitor lizard fighting over a bat.
Even more surprising, over the four months the cameras operated, as many as 214 people approached the cave. They included tourists, staff from a local wildlife research institute, and even children on group tours. There were warning signs about the Marburg virus nearby, but people paid no attention. Only one person wore a mask.
◇ Suspected pathway for Marburg virus spillover
Jonathan Epstein, founder of One Health Science in the United States, told the New York Times that it was "a really important observation, because we usually only speculate about how wild animals interact with each other and rarely observe it directly." Epstein is an expert on viral zoonotic diseases.
Bats do not get sick even if they carry the Marburg virus. But animals or people infected through bats develop deadly hemorrhagic fever. Caves, where bats roost, are a pathway for virus spillover. According to unpublished data from Adam Hume of Boston University School of Medicine, 43% of Marburg cases since 1967 are linked to cave visits.
Researchers with the Kambara Lion Project said the Ugandan cave is also likely a Marburg virus spillover site. In fact, a Marburg outbreak that occurred in 2007 at the Kitaka mine, 50 kilometers from the cave studied this time, was confirmed to have originated from bats in Python Cave. In addition, two tourists who visited Python Cave in 2007 and 2008 were infected with the Marburg virus, one of whom died.
The survivor at the time said the person went about 3 meters into the cave and stayed for around 30 minutes. Jonathan Towner of the U.S. Centers for Disease Control and Prevention (CDC) said tourists might have come into contact with bat droppings in the cave.
After Marburg patients emerged, a sealed observatory was built in 2011, 30 meters from the cave. Signs were also installed to prevent visitors from approaching the cave. But in the footage taken this time, people came within a few meters of the bat-inhabited cave. The researchers said tourists should be provided protective equipment to avoid exposure to the Marburg virus and that wild animals entering and leaving the cave should be tracked and monitored.
◇ A pandemic like COVID-19 could recur
Incidents suspected to be the moment when viruses jump from bats to wild animals have been captured before. In 2024, Tony Goldberg of the University of Wisconsin–Madison School of Veterinary Medicine reported in the international journal Communications Biology that, after more than two years of research in Uganda's Budongo Forest Reserve, he captured footage of chimpanzees eating bat droppings.
In nature, it is not unusual for animals to eat feces. Mother birds swallow droppings as soon as chicks excrete. Pets raised by people also often eat other animals' droppings. But scientists see it differently if what chimpanzees ate was bat droppings, because bats are "hotbeds" of viruses.
Bats carry 137 types of viruses, 67 of which infect humans. Ebola hemorrhagic fever and Marburg fever, as well as rabies and Nipah, originated from bat viruses. The scientific community believes COVID-19 also came to humans when a coronavirus in bats reached people through wild animals that served as intermediate hosts and were trafficked illegally. Severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) were confirmed to have spread to people via other coronaviruses in bats through civet cats and camels, respectively.
The 1995 film "Outbreak" is cited as having foretold the COVID-19 pandemic. The film depicts an employee at a U.S. quarantine station in San Francisco diverting a monkey smuggled from Africa, after which people begin coughing up blood and dying. The monkey was carrying the Ebola virus. The film has already become reality through COVID-19. To prevent another COVID-19, shouldn't we start by restoring the distance between humans and wild animals?
References
Current Biology (2026), DOI: https://doi.org/10.1016/j.cub.2026.02.043
Communications Biology (2024), DOI: https://doi.org/10.1038/s42003-024-06139-z