ST. PAUL — Poultry farmers in Minnesota are cautiously watching the spread of bird flu in Europe and Asia.

The World Health Organization is on “high alert” because the virus has been found in 40 countries around the world since last fall and is spreading quickly.

Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, said the spring waterfowl migration will increase the risk of the virus coming to Minnesota. Outbreaks in 2015 devastated more than 100 Minnesota farms and cost the state economy over $500 million.

The H5 virus family that hit the state two years ago is the most widespread now. But Osterholm said there’s also an H7 cluster in China that is particularly worrisome because it has infected hundreds of humans in addition to birds.

“About 30 to 35 percent of the people who are developing this H7N9 infection are dying,” Osterholm said.

Experts think the virus has been spreading to people from birds, but not from human to human. If person-to-person transmission flares, it could produce an influenza pandemic, Osterholm said.

Glen Taylor owner of Rembrandt Foods, one of the nation’s largest egg producers, said it’s unclear how the virus made its way into the company’s barns in 2015.

Taylor said Rembrandt Foods has taken steps to keep out any new virus. Supply trucks that may visit other poultry farms are strictly controlled, and employees unload at an entrance gate if possible.

“We’ve got more emergency response equipment in the state to be able to react quicker,” said Steve Olson, who heads turkey and chicken trade groups in Minnesota. “There are processes that have been streamlined. I think that’s going to help the situation overall.”

He said Minnesota is much better prepared than it was two years ago, adding that the poultry industry hopes its defenses don’t have to be tested.