Like hundreds of Minnesota turkey growers, Kim Halvorson has watched helplessly as a lethal flu has struck 14 farms and wiped out more than 900,000 birds.

A month into the outbreak, she worries about it in her sleep.

“I had a nightmare where I walked into the barn and every bird was gone,” said Halvorson, who with her husband, Dennis, has raised turkeys for 27 years west of Faribault. “It’s kind of similar to knowing that there is a burglar in the neighborhood, but you don’t know where he’s going to hit.”

Minnesota, home of the nation’s largest turkey industry, is the epicenter of the worst U.S. outbreak of highly pathogenic bird flu in at least 30 years. The avian H5N2 virus touched down in Pope County in early March and has spread quickly in the past two weeks, striking the heart of turkey country in central Minnesota.

Nine Minnesota counties have been hit, with Stearns County suffering four outbreaks. The virus is unprecedented, it can financially devastate farmers and there’s no end in sight to its spread through the state’s $600 million turkey industry.

“You just sit and hope and pray the grim reaper doesn’t knock today,” said Greg Langmo, a turkey grower in Litchfield.

Farmers are trying to seal their barns to keep the bug out. Epidemiological detectives — state and federal animal health scientists — are working overtime. The state Department of Natural Resources (DNR) is scouring waterways near outbreak sites, sampling waterfowl droppings that could prove to be the flu’s source.

The bug is mysterious. It’s believed to originate in wild waterfowl — particularly ducks — who don’t get sick from the virus but spread it through their feces or nasal droppings. Somehow the virus has infiltrated enclosed barns stuffed with thousands of turkeys.

“When you look at a map, you see a lot of turkey farms in Minnesota,” said T.J. Myers, associate deputy administrator in veterinary services for the U.S. Department of Agriculture. “When you look at a map of Minnesota, you also see a lot of lakes.”

The flu’s spread

The H5N2 bird flu has surfaced in at least nine states since late last year, first in the west and then in the Midwest and mid-Southern states. Chickens are susceptible to the bug, too, putting the nation’s huge chicken industry on high alert. But the virus has been particularly deadly to domestic turkeys, and Minnesota produces about 46 million of them a year.

The bird flu outbreak hasn’t yet led to turkey price increases for consumers. Despite the high death toll, only about 2 percent of Minnesota’s annual production has been lost. And the bird flu poses a low health risk to people. So far, there have been no human cases of illness in the U.S. from H5N2.

But once it gets rolling in a turkey barn, birds die quickly and there’s no drug to stop it.

Farmers know the flu’s symptoms. Birds cough. They can lose their appetites. Diarrhea may set in. “The birds seem sedated or depressed,” said Robert Porter, a professor of veterinary population medicine at the University of Minnesota. “They are just unusually quiet.”

The flu takes two to four days to spread within a barn. Most Minnesota turkey farmers operate more than one barn, but in all but one of the 14 outbreaks the virus has appeared in only one barn on each farm site.

However, birds in the remaining barns are killed as a precaution. About two-thirds of the turkey deaths come from such flock culling.

The biggest single loss — 310,000 birds — was at a massive farm in Meeker County owned by Hormel Foods, the Austin, Minn.-based maker of Jennie-O turkey products. The disease hit one barn, but turkeys in all 12 barns on the site are being destroyed.

Hormel is the nation’s second-largest turkey processor, and it relies on Minnesota and Wisconsin for its birds, many of which come from farms it doesn’t own.

Farmers have closely followed bird flu for years as it rolled through Southeast Asia, said John Zimmerman, a turkey farmer in Northfield. “But we never expected it to jump to the Western Hemisphere.”

Scientists believe Asian waterfowl carried a high-pathogenic flu bug over the Bering Strait. They basically ran into North American birds who carried a low-pathogenic avian flu. “There was a mixing where these different viruses came together and created a new virus,” said the U’s Porter.

It landed in Washington, California, Oregon and Idaho first. “We thought it wouldn’t cross the Rocky Mountains,” Zimmerman said. “Now, it’s a new frontier for all of us.”

Farmers hit hard financially

Farmers hit by the flu face a nightmare of financial losses and dead bird disposal.

Insurance against avian disease is scarce, so birds felled by the flu translate into lost income. The USDA indemnifies farmers for birds killed as a precaution. However, “it in no way makes the producer whole,” said the USDA’s Myers. “There is still a huge economic hardship on producers.”

Altogether, the state has about 450 turkey growers who together own about 600 farms, according to the Minnesota Turkey Growers Association.

Many farms are family-owned. “There are a core of familes who have been in this business since the ’30s, ’40s and ’50s,” Zimmerman said. Like other growers interviewed, he knows farmers who’ve been stung by the flu. “We all know everybody. This isn’t a very large industry.”

An outbreak makes a farmer’s barns unusable for weeks, if not months. Under regulators’ protocol, the tainted dead turkeys are “composted” on site, a process that takes four weeks. Once the compost is removed, the barns have to be scrubbed and disinfected. New bedding — wood chips, usually — must be brought in.

Getting new baby turkeys on the fly isn’t easy. Production schedules for 2015 are set, and growers are now ordering their birds for 2016. “Hatcheries aren’t standing around waiting for your call,” said Langmo, who has several turkey growing locations. “I’m telling my people if we get[the flu], we are out of business for six months.”

The virus — apparently via waterfowl feces — is being tracked into farms. The carrier could be a worker’s boot, a truck tire or even a rodent scurrying into the turkey house. So growers are on code red when it comes to biosecurity, restricting access to their barns and arming themselves with disinfectants.

“We’ve stepped it up a notch,” Zimmerman said. Workers on his farm have always cleaned their boots before entering barns. Now, they must put on a separate pair of boots upon entering each of his six barns. “The boots will never go outside,” Zimmerman said. Ditto for coveralls in each barn.

All the changing of boots and coveralls adds about an extra hour of work each day. And Zimmerman said he’s spent about $1,000 over the past two weeks on the new work duds.

The search for the cause

A brigade of animal health scientists are investigating the bug, how it’s traveling and what if anything can stop it. About 40 USDA staffers have come to Minnesota to work with about 20 employees of the Minnesota Board of Animal Health.

The DNR is fanning out over each county, collecting feces samples and looking for any dead wild turkeys or raptors like hawks and falcons. The big birds could eat smaller birds that can get infected. The DNR collected samples from 148 birds — mallards and swans — near the Pope County outbreak. None tested positive for highly pathogenic H5N2.

Waterfowl migrate north to Minnesota from Louisiana, Texas and Mississippi, among other states. In Minnesota, they arrive as ice goes out on lakes, so the migration has been in full swing for weeks.

Thursday, Fred Bengtson, a DNR area wildlife manager, and his crew went looking for duck droppings on the Sauk River in Stearns County. “This is a first for us,” he said. His crew slid their canoe into the winding river just south of New Munich. They were in a “control zone,” a 6-mile area around an infected farm.

State law forbids naming the exact location or name of a turkey farm hit by the disease, animal health regulators say. But there are three turkey farms within a few miles of where the DNR was sampling. One farm, just up the Sauk River near Melrose had a prominently posted sign out front.

It said: “KEEP OUT. Disease Control.”