Deer With Tumor-Like Growths Spark Outbreak Fears Across the U.S.

After sightings of rabbits and squirrels with tumor-like growths, deer with similar deformities have recently been spotted across New York, Pennsylvania, and Wisconsin, alarming residents.

Photos shared online show white-tailed deer covered in large lumps. “A white-tailed deer in Pennsylvania. But what is the growth? Is it a mole? A boil? An injury?” one Reddit user asked earlier this month.

Wildlife officials have since identified the cause as deer cutaneous fibroma, or deer warts—a condition triggered by a virus commonly spread among deer populations throughout the U.S.

The virus is transmitted primarily by mosquitoes and ticks that feed on infected animals and then bite healthy ones. It can also spread through direct contact between deer or contaminated surfaces. The disease belongs to the same family of papillomaviruses that affect humans, though people cannot catch deer warts.

However, experts warn that ticks carried by deer can transmit other diseases, such as Lyme disease, to humans. “Temperature changes are resulting in diseases that were never endemic in certain areas to become endemic,” said Dr. Omer Awan of the University of Maryland School of Medicine.

He noted that Lyme disease is now being reported farther north, including in southern Canada and northern U.S. states like Maine, as climate shifts allow ticks to thrive in new regions.

According to Metro, the fibromas usually appear on the deer’s neck, head, and forelegs. They do not cause pain but can interfere with sight, eating, or movement. Most growths eventually dry up and fall off naturally within a few months.

Experts emphasize that while social media has brought more attention to the condition, deer cutaneous fibroma has existed in the U.S. for decades—likely since the 1950s.