SIOUX FALLS, S.D. — Five commercial turkey farms in South Dakota have now been infected with a bird flu strain that’s led to the deaths of more than 250,000 turkeys in the state and over 2.4 million birds in the Midwest.

The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service announced Friday that the H5N2 strain of avian influenza in a flock of 66,000 birds in a Roberts County farm in the far northeastern corner of the state, marking South Dakota’s largest outbreak to date.

The approximately 6-mile quarantine zone that officials set up around the impacted farm also stretches into parts of North Dakota and Minnesota. Dr. Dustin Oedekoven, the South Dakota state veterinarian, said Thursday that crews were beginning to euthanize the farm’s surviving birds to prevent the disease from spreading.

The commercial turkey farm is the latest in the region to be hit with the disease that has cost producers millions of birds since early March. Dr. John Clifford, the USDA’s chief veterinary officer, told The Associated Press on Thursday the nation’s poultry industry may have to live with the deadly bird flu strain for several years.

Once response teams have “depopulated” the Roberts County farm, approximately 256,000 turkeys in South Dakota will have died as a result of the disease. While that’s a considerable chunk of the approximately 4.5 million turkeys the state’s Hutterite growers produce annually and a severe loss to individual producers, Oedekoven said it shouldn’t threaten the overall health of the state’s industry.

“So, it’s not good, but it’s not going to put anybody out of business,” said Jeff Sveen, board chairman for Dakota Provisions, a farmer-owned plant that processes the birds raised by the state’s 42 turkey farms.

As the weather gets warmer and drier, the virus won’t survive as well. Experts warn that producers should be wary of symptoms they notice in birds, such as ruffled feathers or discharge from beaks.

“But with this particular strain, the most obvious sign is: they’re dead. They’re suddenly dead,” Oedekoven said.

Even if producers only have a dozen birds, Oedekoven said they should still alert state veterinary officials if they notice an unusual drop.

“The sooner we know about it, the sooner we can attempt to do something about it,” he said.