Why ‘Zombie Squirrels’ Have Been Appearing In The U.S. And Canada

News of “zombie squirrels” appearing in the U.S. and Canada may be a bit shocking. (Photo: Getty)

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The idea of “zombie squirrels” may seem a bit nuts to you. But that’s the term that people have been using to describe what they’ve been seeing in the U.S. and Canada— squirrels with strange, at times bleeding, lumps all over their bodies. These lumps can make them look a bit like the characters seen on the TV series Walking Dead—the undead ones without speaking parts, that is. Except these squirrels aren’t actually undead. They’re very much alive but probably suffering from what’s called squirrel fibromatosis.

Zombie Squirrels Are Actually Squirrels With Tumors

It’s called fibromatosis because the lumps are tumors called fibromas. A fibroma is a non-cancerous tumor consisting of fibrous connective tissue. These tumors can range from few millimeters to 25 millimeters in diameter. The impact of these growths depends on where the tumors are situated. In many cases, when these tumors are just on the squirrel’s skin, they won’t have major serious consequences, except perhaps affecting the squirrel’s ability to get dates, assuming that other squirrels are as superficial as humans.

However, things can get squirrely when the tumors impinge upon vital structures. For, example, tumors close to the eyes can affect the squirrel’s vision. Things can get worse when the tumors spread inside the body like to the lungs, liver, kidneys and lymph nodes. There they can cause obstruction of different body passageways, organ malfunction and even death. Another risk is that such lumps can get infected by various microorganisms beyond the microorganism that caused the fibromatosis in the first place.

Zombie Squirrels Result From Infection By A Virus

News of these zombie squirrels may have gone viral. But there is something else viral about this disease— its cause. Infection with a virus called leporipoxvirus leads to these tumors. This virus belongs to the pox group of viruses. That’s why squirrel fibromatosis is also known as squirrel pox.

Squirrels can catch this virus by being bitten by mosquitoes like Aedes aegypti and Anopheles quadrimaculatus or fleas carrying the virus. An infected squirrel can also pass along the virus to another squirrel by direct physical contact. Tumors typically first develop where the transmission of the virus occurred whether it’s via an insect bite or direct squirrel-to-squirrel contact.

Is There A Treatment For Zombie Squirrels?

Unfortunately, there’s no treatment for this disease. Fortunately, though, when the disease is not severe, the lesions can end up regressing over time, and the squirrels can ultimately fully recover. Plus, there hasn’t been evidence that this disease is affecting the North American population numbers of grey squirrels, the type of squirrels currently being affected, according to the Michigan Department of Natural Resources.

This disease isn’t new, either. Squirrels with this ailment have been spotted ever since at least 2023. It’s just that for whatever reason more humans have been noticing such zombie squirrels recently and commenting about them on social media. And things aren’t real until they’ve reached social media, right?

Do Zombie Squirrels Pose A Threat To Humans?

You may have to worry about getting infected with the leporipoxvirus if you happen to be a squirrel or potentially a rabbit or woodchuck. While the only documented transmission in nature has been to squirrels, transmission to rabbits and woodchucks have occurred in laboratory settings. If you are not sure whether you are one of these animals, check yourself in the mirror, contact your doctor, ask yourself if anyone has remarked how long your ears are or see how annoyed you get when you hear the question, “How much wood can a woodchuck if a woodchuck would chuck wood?”

If, on the other hand, you are human, then there doesn’t seem to be a risk that you will get infected. This may even be the case if you happen to eat an infected squirrel. This doesn’t necessarily rule out the possibility of the virus mutating some day to infect humans. But for now if you see a “zombie squirrel,” there’s no reason to run from it like you would from a human zombie.