‘Zombie squirrels’ covered in gory sores have been turning up in backyards and at animal sanctuaries in the US, sparking concern online.

Though alarming to look at, the animals don’t pose a threat to humans or most pets.

Photos of the rodents circulating on social media platforms like Facebook, X, and Reddit seem to depict animals afflicted with squirrel fibromatosis, commonly known as squirrelpox.

A common skin disease among grey squirrels in the US, squirrel fibromatosis is caused by leporipoxvirus.

The virus causes hairless growths or tumours which can turn into open sores.

These growths don’t typically affect a squirrel’s ability to survive unless, as in some rare cases, they spread to the animal’s internal organs.

This can leave them weak and lethargic but death is rare.

Squirrel fibromatosis is spread through contact between healthy squirrels and the saliva or lesions of infected squirrels.

Common exposure sites include bird feeders set up by humans that multiple squirrels feed from.

Fortunately, for US residents who have noticed infected squirrels in their yards, this virus cannot be transmitted to humans or common pets like cats and dogs.

That being said, Shevenell Webb of Maine’s Department of Inland Fisheries and Wildlife said residents should not interact with infected animals.

“It is naturally occurring and will run its course in time.”

Cases of squirrel fibromatosis have been reported across the US for years and these new sightings fit with seasonal trends in rates of infection.

It’s crucial to understand that while squirrel fibromatosis is often called squirrelpox in the US, it is a completely different virus from the UK squirrelpox, which poses a lethal threat to red squirrels.

Dubbed ”Frankenstein bunnies,” “demon rabbits” and “zombie rabbits” online, they too were suffering from a relatively common virus.

They were infected with the mostly harmless Shope papillomavirus, which causes wart-like growths that typically clear up over time.