SIOUX FALLS, South Dakota — A bird flu strain that’s deadly to poultry has spread to a second turkey farm in one of the top turkey-producing counties of Minnesota, state and federal officials said Thursday.

The U.S. Department of Agriculture confirmed the H5N2 strain in a flock of 71,000 turkeys in Stearns County, the Minnesota Board of Animal Health said. That brings the number of Minnesota turkey farms where the strain has been detected to five, officials said.

The strain also has shown up in a commercial turkey flock in South Dakota. So far, the total number of outbreaks in the Midwest has reached 10 and led to the deaths of 314,000 birds since early March.

Earlier, the USDA confirmed the H5N2 strain in a flock of 53,000 turkeys in Beadle County of eastern South Dakota, and a fourth Minnesota case in the southwest part of the state, in Nobles County, involving a commercial turkey farm with about 21,000 birds.

Following the same protocols used at other infected farms, the surviving birds at the operations have been quarantined and will be killed to prevent the disease’s spread. Any nearby poultry farms will be checked.

While officials have stressed there’s little danger to public health and no food safety concern, they’ve monitored workers at the affected farms as a precaution. No human H5N2 infections have been reported in the U.S., although the Centers for Disease Control and Prevention said similar viruses have been detected in people in other countries.

The infected South Dakota flock is on Riverside Farms near Huron, one of several Hutterite colonies that own and supply turkeys to Dakota Turkey Growers LLC.

“It’s extremely frightening, to be honest with you,” Dakota Turkey Growers president and CEO Ken Rutledge said. “We were hopeful we’d be able to get through this without having a break in the state.”

The birds killed by the virus or euthanized represent just a sliver of the overall U.S. turkey production — 235 million birds in 2014, according to USDA statistics.

Experts say U.S. consumers likely will benefit from lower turkey prices eventually because poultry that would have been exported will have to be sold instead on the domestic market. More than 40 countries have imposed import restrictions since late last year. Some bans are limited to the affected states or counties, while China cut off all poultry shipments from the U.S.

Minnesota — the nation’s top turkey-producing state — was the first state to see the H5N2 strain in the Mississippi Flyway, a major wild bird migration route. The state’s first case was confirmed March 4, followed by flocks in Arkansas and Missouri. Kansas was the first to see H5N2 in the Central Flyway when the virus was confirmed in a backyard chicken and duck flock on March 13, now followed by South Dakota.

The same virus and other highly pathogenic H5 bird flu strains also have turned up in commercial and backyard flocks and wild birds in the Pacific Flyway since late last year.

Experts say turkeys appear to be particularly susceptible to this virus, but chickens and other species are not immune. Montana’s first recorded case this week was confirmed in a captive falcon.

Most commercially grown turkeys and chickens in the U.S. spend their entire lives indoors to keep them away from waterfowl and other wild birds that could introduce diseases. Migratory ducks and geese don’t normally become sick from bird flu, but can spread viruses via droppings, which farm workers and rodents can then track into barns.

Biosecurity has been stepped up at farms across the Midwest in recent weeks in response. The outbreaks have been a particular concern in Minnesota — which has had the most cases in the region and lost 170,000 turkeys. The affected turkey farms in Missouri lost 51,000 birds, the while one in Arkansas lost 40,020. Kansas officials have refused to release their losses.