(NewsNation) — Nearly 1 million chickens on a Minnesota egg farm have contracted the bird flu, the U.S. Department of Agriculture reported this week. Under federal guidelines, they were killed to prevent the spreading of the highly contagious disease.

The USDA reports the virus was found at a farm in Wright County, Minnesota, as well as in three smaller flocks in South Dakota and Iowa. Whenever the highly pathogenic avian influenza virus is detected on a farm, the entire flock is killed to keep it from spreading to other farms.

According to USDA data, 26,800 turkeys were killed on a farm in McPherson County in South Dakota and nearly 17,000 birds will be slaughtered on two farms in Iowa’s Clay County.

The egg and poultry industry has been dealing with a bird flu outbreak since last year. In 2022, nearly 58 million birds — mostly chicken and turkeys — were slaughtered to deal with the virus, contributing to significantly higher egg and turkey prices.

The Minnesota farm is the first egg-laying operation where bird flu has been found this year.

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The toll overall has been much lower in 2023 than in 2022, as the number of cases found in wild birds plummeted and farmers redoubled their efforts to prevent any contact between their birds and the ducks and geese migrating past their farms. Even after 940,000 chickens on the Minnesota farm are slaughtered, there will only have been about 3.4 million birds killed this year.

Minnesota has now lost a total of more than 5.5 million birds since the outbreak began.

Egg and poultry farmers take steps like requiring their workers to change clothes and sanitize their boots before stepping inside their barns, limiting the sharing of tools between barns and sealing up their facilities to prevent wildlife from getting inside.

Officials stress that bird flu isn’t a threat to food safety because all the birds on a farm where the disease is found are slaughtered before they reach the food supply, and properly cooking poultry and eggs to 165 degrees Fahrenheit will kill any viruses. Infections in humans are rare and usually come only in people with prolonged exposure to sick birds.