Overview

• Photos on Reddit and X show gray squirrels with pus-filled, wart-like tumors surfacing this summer across Maine, other U.S. states and parts of Canada.
• Wildlife experts diagnose the lesions as squirrel fibromatosis, a viral skin disease caused by leporipoxvirus rather than the squirrelpox seen in UK red squirrels.
• The virus transmits through direct contact with lesion fluid or saliva, and shared bird feeders concentrate squirrels and amplify spread.
• Authorities stress the disease cannot infect humans, dogs or birds and warn against capturing or handling visibly infected squirrels.
• Most affected squirrels recover within four to eight weeks as their immune system clears the virus, though severe internal infections can prove fatal.