The virus that typically causes fibromas in deer isn't new and poses no threat to people. It typically doesn't cause significant harm to the animals, either. Additionally, wildlife officials in Pennsylvania and Wisconsin haven't noted an uptick in reports of deer fibromas.

In August 2025, unsettling photos of so-called "mutant deer" with growths on their skin circulated on social media, sparking fears of a widespread disease outbreak. Posts sharing the photos claimed these deer with "flesh bubbles" had been spotted in multiple states.

"'Mutant deer' spotted with eerie flesh bubbles increases fear of an animal outbreak in the US: 'This is the kind of stuff you see in zombie movie intros where they say it started out slowly,'" an Aug. 21 Facebook post (archived) read. Another post (archived) claimed deer were "showing signs of widespread disease."

Multiple Snopes readers also searched our website and emailed us asking for information about the supposed "mutant deer."

There are real viruses that can cause wartlike growths, called fibromas, in deer, according to various wildlife experts. However, social media users' fears were overblown.

The virus that typically causes fibromas in deer isn't new and poses no threat to people. It typically doesn't cause significant harm to the animals, either. Additionally, wildlife officials in Pennsylvania and Wisconsin haven't noted an uptick in reports of deer fibromas.

Fibromas in animals are caused by species-specific poxviruses and papillomaviruses, Cornell University's Wildlife Health Lab explained. The viruses are typically transmitted by biting insects like fleas and mosquitoes, and direct contact with injured skin.

Because the viruses that cause fibromas are specific to certain wildlife species, the growths cannot be transmitted to humans, the lab adds.

In deer, fibromas are typically caused by infections with a specific papillomavirus, according to Maine's Department of Fisheries and Inland Wildlife. The department emphasized that the virus poses no risk to people, pets or livestock, writing:

The virus that causes deer fibromas is not known to infect humans. Fibromas are caused by a papillomavirus, which are species specific. Though similar diseases exist in other species, deer will not spread their fibromas to pets, livestock, or other species.

The New York Department of Environmental Conservation also confirmed via email that "this virus does not infect humans or pets."

The wartlike growths can appear on any part of an animal's body, but they are usually found on its head and legs, Cornell's Wildlife Health Lab said.

Similar fibroma diseases also occur in other species, such as squirrels and rabbits. For example, Snopes previously reported on the Shope papillomavirus that infects wild rabbits, and causes tentacle- or hornlike growths on their skin. We found that the virus in rabbits also poses no threat to other species, including humans.

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Wildlife agencies in Pennsylvania and Wisconsin told us reports about fibromas in deer are common, but neither state was aware of a notable increase in reports in recent months.

"We have not had an uptick in these reports, though they are very common and most years we receive a number of reports about them," a spokesperson with the Wisconsin Department of Natural Resources said via email.

The agency noted it had received reports about deer with fibromas in 2025, noting that they usually "pick up once the rut and hunting season starts."

Travis Lau, a spokesperson for the Pennsylvania Game Commission, said few deer among the population have fibromas, but the agency does receive reports about them "fairly regularly," often from people seeing them for the first time. He added that he was "not aware of any increased reports of fibromas in Pennsylvania."

The New York DEC did not address questions about whether it had seen an uptick in reports of deer fibromas. However, the agency did direct us to what appeared to be the source of a photo used in many of the 2025 social media posts. The Ohio Division of Wildlife posted (archived) a photo of a deer with fibromas on Twitter, now X, in 2017.

Fibromas are usually harmless to deer unless the animal has a severe case that compromises its ability to see, eat or move, according to Lau and the Maine Department of Inland Fisheries and Wildlife.

There isn't an effective treatment for fibromas, the Pennsylvania Game Commission said. Deer with immune symptoms that function well usually fight off the infection on their own and the fibromas eventually go away, according to the commission and the Wisconsin DNR.

Deer with fibromas can usually live normal lives and should be left alone, wildlife experts say. But if the fibromas appear to be negatively affecting a deer's health, you can contact wildlife authorities in your state.

An infected animal's meat is safe to eat, experts say, but anyone with health and safety questions should also contact their local wildlife authorities.

There are real viruses -- typically, a specific papillomavirus -- that can cause wartlike growths called fibromas on deer. However, the virus doesn't pose any dangers to people, pets or livestock.

Fibromas are often harmless to deer, too, unless they have a severe case that affects their ability to see, eat or move, experts say.