Zombie-esque squirrels covered in oozing, wart-like tumors have been invading backyards across the United States and the reason behind the deformities is likely caused by the species’ version of herpes, according to experts.

The grotesque-looking gray squirrels have been increasingly photographed this summer in US states, including Florida, North Carolina, and Michigan, the Daily Mail reported, citing a flurry of social media posts reporting the bizarre sightings.

“What is going on with the squirrels lately?! This is the third one I’ve seen looking like this, and it’s honestly freaking me out,” one user posted on Facebook on June 9, alongside a photo of a squirrel covered in hairless patches and gnarly warts.

A Tarpon Springs, Florida resident also captured a photo of one of the rodents with “patchy fur and reddish bumps.”

“Found this poor squirrel in my back yard, really scared the crap out of me because I could tell it looked deformed,” an Ohio resident added in a separate post of a skulking squirrel covered in warts.

Wildlife experts said the so-called “zombie squirrels” are actually likely suffering from squirrel fibromatosis — a viral skin disease caused by leporipoxvirus, the outlet reported.

The virus spreads through direct contact between healthy squirrels and the lesions or saliva of infected squirrels — mimicking herpes transmission in humans.

The virus is often confused with squirrelpox, which is more common in the UK and can be fatal to red squirrels.

Leporipoxvirus leads to wart-like tumors that ooze fluid. The skin condition often clears up on its own, but in severe cases, the growths can affect internal organs and lead to death.

A surge in sightings of Leporipoxvirus-infected squirrels also occurred in August 2025, with notable spikes in states like Maine and across parts of Canada.

Shevenell Webb of Maine’s Department of Inland Fisheries and Wildlife previously told the Bangor Daily News that residents do not need to fear the squirrels, as they pose no threat to humans, pets, or birds.  

“It’s like when you get a large concentration of people. If someone is sick and it’s something that spreads easily, others are going to catch it,” Webb said.

The concentration of spottings could be due to bird feeders, where infected animals expose other squirrels to the virus by leaving saliva or other fluids on uneaten seeds.

People should let the animals heal on their own as the tumors often resolve within four to eight weeks, according to experts.