The U.S. Department of Agriculture detected traces of highly pathogenic bird flu in commercial poultry flocks in South Dakota and Utah on Friday, raising concerns about possible future outbreaks across the country.

So far, virus detections in 328 commercial flocks and 516 backyard flocks in the U.S. have affected 58.97 million birds nationwide. Backyard flocks are residences that keep 1,000 or fewer birds, whereas commercial flocks exceed that amount, according to the USDA.

On Oct. 4, officials in South Dakota confirmed the presence of bird flu among a commercial turkey flock in Jerauld County. More than 47,000 poultry were believed to be affected by the outbreak and will have to be culled. Infected flocks are killed to prevent the spread of the virus.

“I don’t doubt that we will have more cases,” South Dakota State Veterinarian Beth Thompson told The Associated Press. “I would be very pleasantly surprised if we’re done because migration is just starting.”

Two days later, officials identified another infected commercial flock of 134,200 turkeys in Sanpete County, Utah.

The detections are the first cases of bird flu in a U.S. commercial flock since April when the virus was confirmed in a Beadle County turkey farm with more than 75,000 birds and a 58,500-head turkey farm in North Dakota on the same day.

Before the October cases, the only recent reports of bird flu in the U.S. were sporadic in backyard flocks or among wild birds, according to the AP. While wild birds often show no symptoms of avian influenza, infections in them are a concern to the poultry industry because migrating birds can spread the disease to vulnerable commercial flocks.

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Bird flu in the Dakotas

The virus was detected in three commercial bird farms in South Dakota this year, and producers have depopulated more than 123,000 birds. Since the start of the current outbreak, more than 4 million birds have been impacted in the state.

Virus detections in South Dakota tend to affect commercial flocks smaller than 100,000 birds, but Flandreau-based Dakota Layers, a commercial egg-laying operation, was forced to cull 1.35 million hens in December after bird flu was detected on the premises, which made it the 13th highest depopulation event since the start of the current outbreak.

Bird flu proved more devastating to South Dakota poultry farms in 2022. According to The Argus Leader, bird flu affected more than 3.96 million birds last year, more than double the number of flu-hit South Dakota poultry during the 2014 to 2015 outbreak.

Can humans get bird flu?

The Centers for Disease Control and Prevention says bird flu primarily strikes animals, but it has been detected in at least four human cases in the United States. An 11-year-old girl died of the flu in Cambodia in late February, and the country reported its third human death this year due to the virus, according to AP.

The viruses circulating in birds in the United States are believed to be low risk to people, but those working with birds should take appropriate precautions, the CDC recommends. Human cases are extremely rare and none of the infected birds are allowed into the nation’s food supply. And properly cooking poultry to 165 degrees Fahrenheit will kill any viruses, officials said.

Since January 2022, 11 cases of H5N1 have been reported in people. The first 10 were exposed to poultry. 

Symptoms of the illness, according to the CDC, include eye redness, flulike upper respiratory symptoms that range from mild to severe, fever, and body aches.

Avian flu costs the U.S. millions

The ongoing bird flu outbreak has cost the government roughly $660 million and added to consumers’ pain at the grocery store after more than 58 million birds were slaughtered earlier this year to limit the spread of the virus. This is the country's deadliest outbreak, according to USDA figures.

50.6 million birds across 15 states were affected in the U.S. during the 2014 to 2015 outbreak, according to the USDA. The events were deemed the most expensive animal health disaster in U.S. history with the government paying over $1 billion to deal with the infected birds and to decontaminate farms, AP reported.

The recent outbreak has cost the industry roughly $3 billion as farmers incurred additional costs and lost money when they didn’t have any birds on their farms.

Agriculture officials consider this year’s cases to be part of last year’s outbreak, which reached the U.S. in February 2022 after spreading in Europe. The U.S. has imposed periodic restrictions on poultry imports from Europe to limit the potential for spread. Thompson said the virus never completely went away, unlike in 2015, and that the version now circulating is essentially the same that spread last year.

“We're just encouraging bird owners to make sure they’re increasing their biosecurity practices because avian flu is still out there and it’s easy to contract,” said Bailee Woolstenhulme, spokesperson for the Utah Department of Agriculture and Food.

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Contributing: The Associated Press

Dominik Dausch is the agriculture and environment reporter for The Argus Leader, part of the USA TODAY Network. Follow him on X and Facebook @DomDNP and send news tips to [email protected].