Do Squirrels Carry Disease?

Squirrels are not known for causing any specific diseases in humans. However, this may be due to the fact that most people don’t come into direct contact with them. Eastern gray squirrels have been found to carry some types of infectious fungi on their fur, skin, and toenails, including a fungus responsible for causing ringworm.1,2 Some other diseases that have been studied in relation to squirrels are West Nile virus, Lyme disease, and the squirrel parapoxvirus.

West Nile Virus and Squirrels3

Squirrels, specifically fox squirrels, western gray squirrels, and our favorite eastern gray squirrels, have been known to fall ill and even die from West Nile virus. Signs that a squirrel might be infected include foot biting, clumsy movements, turning in circles, shaking, and acting fatigued. Even though West Nile virus is usually transmitted through mosquito bites and doesn’t cause illness in most people,4 it’s still best to avoid contact with any squirrel engaging in the previously described behaviors.

Lyme Disease and Squirrels5

Most eastern gray squirrels carry the bacteria that cause Lyme disease. However, squirrels don’t get sick with Lyme disease themselves nor can they pass it directly to other animals. Lyme disease is only transmitted through tick bites. To protect your health when handling squirrels, first check them for ticks or other parasites.


Living in an area with a lot of eastern gray squirrels can actually decrease your chances of getting Lyme disease! That’s because the majority of ticks pick up the Lyme bacteria from mice, so if more ticks are feeding on squirrels, fewer of them will actually become carriers for this disease.

Parapoxvirus and Squirrels6

Eastern gray squirrels can carry a type of virus called a parapoxvirus. Though this parapoxvirus seems to have little to no effect on the gray squirrels, it’s known to infect and kill red squirrels in the UK. Gray squirrels are indigenous to the eastern part of North America7 and are actually seen as pests in the UK, in part because they’re replacing native red squirrel populations. The squirrel parapoxvirus does not affect humans.

The bottom line is that care should be taken when handling squirrels. Remember, all wild animals can carry bacteria or viruses which can then be transmitted to any people who come into contact with them.

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1 Lewis, E., Hoff, G., Bigler, W., & Jefferies, M. (1975). Public health and the urban gray squirrel: mycology. Journal of Wildlife Diseases, 11(4), 502-504. Retrieved from

2 Centers for Disease Control and Prevention. (2015). Diagnosis of ringworm. Retrieved from

3 Padgett, K., Reisen, W., Kahl-Purcell, N., Fang, Y., Cahoon-Young, B., Carney, R., Anderson, N., Zucca, L., Woods, L., Husted, S., & Kramer, V. (2007). West Nile virus infection in tree squirrels (Rodentia: sciuridae) in California, 2004 – 2005. The American Journal of Tropical Medicine and Hygiene, 76(5), 810-813. Retrieved from

4 Centers for Disease Control and Prevention. (2015). West Nile virus. Retrieved from

5 Dobson, A., Cattadori, I., Holt, R., Ostfeld, R., Keesing, F., Krichbaum, K., Rohr, J., Perkins, S., & Hudson, P. (2006). Sacred cows and sympathetic squirrels: the importance of biological diversity to human health. PLOS Medicine. Retrieved from

6 Tompkins, D., Sainsbury, A., Nettleton, P., Buxton, D., & Gurnell, J. (2002). Parapoxvirus causes a deleterious disease in red squirrels associated with UK population declines. Proceedings of the Royal Society B: Biological Sciences, 269(1490), 529-533. Retrieved from

7 Jackson, T. (2006). The illustrated encyclopedia of animals of America. London: Lorenz Books.