Highly lethal bird flu is taking on epidemic proportions, hitting eight more Minnesota turkey farms and bringing the number of birds affected in the state to more than 1.4 million.

The newly afflicted farms were raising more than 500,000 turkeys, making Tuesday’s announcement by regulators the largest one-day death toll since highly pathogenic H5N2 bird flu struck the state in early March. Birds on a farm that don’t die from the sickness are killed as a ­precaution.

Minnesota, the nation’s largest turkey producer at 46 million birds annually, is the epicenter of a nationwide outbreak of the deadly bird flu, which has hit at least 12 states. The first case in Iowa was announced Tuesday, South Dakota has had three outbreaks, and North Dakota and Wisconsin one each.

“It’s clearly a major epidemic,” said Michael Osterholm, a prominent infectious diseases expert at the University of Minnesota. A highly pathogenic bird flu outbreak this large is “unprecedented” in the United States, he said.

And it’s likely not going away soon. “We do expect to see additional [flocks] affected through this spring,” said Bill Hartmann, chief veterinarian for the Minnesota Animal Health Board.

Still, animal health experts hope that the warmer spring weather will stop the virus, which likes cold and damp weather.

The bird flu is believed to be spread by waterfowl that carry the virus but don’t get sick from it. Domestic turkeys are highly susceptible to the flu, and chickens have caught it, too.

However, the H5N2 virus has yet to cause human illness in the United States, health experts say. “This is not a public health risk or food safety risk,” said Ed Ehlinger, commissioner of the Minnesota Department of Health.

Still, people in other countries who work closely with infected birds have caught strains of highly pathogenic avian flu.

The state Health Department has been monitoring 60 people who’ve worked on infected farms, and none of them has come down with the flu, Ehlinger said.

The bird flu has rocked the state’s turkey industry, which includes about 450 growers who tend about 600 farms. “Highly pathogenic avian influenza is a game changer,” said Steve Olson, executive director of the Minnesota ­Turkey Growers Association.

Likening the flu’s spread to tornado season, Olson said that “for turkey farmers, it’s like a 24-hour, seven-day-a-week tornado warning that lasts for two months.” And even if warm weather stops the bug, it’s not over for the turkey industry.

With the flu ingrained in turkey country, farmers will have to be on guard against the virus for the next three to five years, Olson said.

For farms hit by the flu, the financial and emotional toll is “devastating,” Olson said. The birds killed in the first 14 outbreaks cost farmers nearly $16 million, the growers association said. That doesn’t account for other lost revenue: Barns hit by the flu can be out of commission for months.

Austin-based Hormel Foods, owner of the well known Jennie-O brand, relies on Minnesota and Wisconsin for its turkey supply.

Seven of the eight afflicted Minnesota farms announced Tuesday are suppliers to Hormel, the nation’s second largest turkey processor. In total, 14 of the 22 Minnesota farms hit so far by the highly lethal flu are Hormel suppliers.

The biggest outbreak announced Tuesday hit two Hormel-affiliated farms in Swift County with a total of 314,000 birds. Other outbreaks reported Tuesday:

• A 76,000 turkey flock in Stearns County, the fifth bird flu incident in that county.

• A 56,000 turkey flock in Redwood County.

• Two farms in Meeker County totaling 45,000 birds, the second and third incidents in that county.

• A 30,000 turkey flock in Kandiyohi County, the fourth incident there.

• A 21,500 turkey flock in Le Sueur County.

State law forbids naming the exact location or name of a turkey farm hit by the disease, animal health regulators say.

Hartmann said there are now 130 people in Minnesota working on solving the bird flu, including researchers and other personnel from the ­animal health board, the state Agriculture Department and the U.S. Department of Agriculture. They’ve yet to figure out exactly how the bug is getting into enclosed turkey barns with biosecurity precautions against disease.

Meanwhile, the Minnesota Department of Natural Resources is in the midst of taking 3,000 wild waterfowl feces samples throughout the state, trying to find the virus in nature. With about 350 samples so far, they haven’t had a positive test yet.