Disproving the notion that warmer weather would kill off the bird flu, the virus keeps wiping out poultry flocks in Minnesota, the latest a pullet farm in Renville County with 415,000 chickens.

It's the first time the flu has hit a Minnesota pullet operation, though a dozen Iowa pullet farms — with a total of nearly 5 million birds — have been stricken. Pullets are young hens not yet laying eggs, and their demise could complicate rebuilding the Upper Midwest's battered egg business.

The lethal H5N2 bird flu has claimed 45 million chickens and turkeys nationwide, the majority of them in Iowa and Minnesota.

Minnesota animal health authorities Wednesday said that in addition to the pullet farm, another turkey farm in Renville County had been stricken, bringing the total number of farms to 106. Nearly 9 million birds have been killed in Minnesota, the majority of them turkeys.

Scientists are still scrambling to figure out how the bird flu has spread, but they believed that warmer weather would quash the flu at least until the fall. Indeed, the Minnesota Board of Animal Health did not disclose any new bird flu cases from May 15 through May 25, the longest period free of outbreaks since mid-March.

But since May 26, another 18 cases have been reported in Minnesota, and outbreaks continue to be steadily reported in Iowa, too. On Tuesday, Iowa disclosed that a pullet farm with 1.1 million hens had been hit. Pullet farms get day-old chicks from hatcheries, and raise them for about 17 weeks before the hens are sent to egg-laying operations.

As flu-afflicted chicken and turkey farms begin to repopulate their barns with live birds, they will be looking to suppliers of pullets and turkey poults.

"I think [the stricken pullet farms] will slow down the repopulation process," said Maro Ibarburu, a business analyst at Iowa State University's Egg Industry Center. "We really need these pullet houses."

Turkey farms that raise poults also have been hit by the flu. Still, Steve Olson, head of the Minnesota Turkey Growers Association, said farmers should be able to get young birds.

"On the turkey side especially, I think there will be enough poults to repopulate," he said.

Mike Hughlett • 612-673-7003