Heightened concerns about the potential threat of bird flu have prompted Massachusetts officials to warn the state’s poultry farmers to take precautions to ensure that their flocks don’t contract a virulent strain of avian flu that has turned up in the U.S.

The bird flu led to the deaths of millions of birds earlier this year in the Midwest and on the West Coast. Agricultural officials worry that geese and other waterfowl carrying the virus may have brought the highly contagious disease to Massachusetts while migrating in recent weeks from northern Canada, the Boston Globe reports.

Officials are warning the owners of poultry farms to monitor their chickens, turkeys, and other birds to quickly identify any that appear sick.

“We’re building a plan to respond aggressively to eradicate the disease quickly, so we can minimize its spread and impact,” said Kurt Schwartz, director of the Massachusetts Emergency Management Agency, which has been working with other state departments on plans to contain any outbreak. “This is a very serious concern, because of the potential impacts of the disease and because the response is going to require substantial resources.”

If even one bird is found with avian flu, a poultry farm would be required to destroy its entire flock.

Unlike other strains of the disease, there have been no reports of this strain infecting people, but the risk that it could jump from birds to humans is always a fear.

More than 48 million birds were killed between last December and June after the avian flu ravaged poultry farms in 15 states, according to the U.S. Department of Agriculture.