The men charged with ridding the farm of a deadly contagion tugged at their dark green protective suits and adjusted the double-intake respirators covering their faces.
"Biosecure. Stop!" read a sign at the farm entrance.
Another sign, in red letters, advised, "All employees & drivers must disinfect tires."
Just past the checkpoint sat Rose Acre Farms, a family-owned egg-laying facility that is one of dozens of poultry farms hit hard by the worst avian influenza outbreak in U.S. history.
The jumpsuits, quarantine zones and bleach for disinfecting are among the tools officials in Iowa, the nation's top egg-producing state, are using to halt the spread of the disease.
Rose Acre Farms, which has 17 facilities across six states, said it would euthanize about 1.5 million chickens here in Winterset, a town of about 5,100 best-known as the birthplace of John Wayne. Dozens of gas canisters were lined
up on the farm's muddy driveway Thursday morning as part of the eradication plan.
"Don't get too close," a sentry in a white jumpsuit cautioned.
Entire flocks are killed with carbon monoxide gas, according to the U.S. Department of Agriculture, regardless of how many birds on a farm are actually infected. Some are killed with foam.
The USDA has reported more than 160 cases involving three deadly strains of bird flu since December. About 40% of Iowa's egg-laying hens — about 25 million birds — are dead or will be euthanized. The total nationwide, so far: 33.5 million chickens, turkeys and ducks.
The economic impact of the outbreak is uncertain, industry experts say, though consumers might see some increase in prices.
Iowa's first case of bird flu was discovered last month. In the weeks since, 44 cases of the illness have been reported and the governor has declared a state of emergency.
Quarantine zones, anywhere within a 6.2-mile radius of an infected site, restrict the movement of poultry and poultry-moving equipment. Some counties, such as Buena Vista and Sioux in northwestern Iowa, are almost entirely covered in quarantine zones.
With Iowa producing nearly 15 billion eggs a year, the number of birds to be disposed of is among the biggest challenges.
Bulldozers have carved out giant rectangular pits to bury carcasses, and movable incinerators are being brought into the state.
Sometimes, owners take a little too long deciding how to dispose of the mounds of bodies. State Sen. David Johnson said neighbors complained about a putrid odor after the outbreak hit an Osceola County farm.
"There were about 1 million birds dead or dying out of nearly 4 million that had not been moved yet," Johnson explained. "At first the owner resisted the idea of disposing the birds on his own property … but now they're composting."
Before the owner decided on composting, however, Johnson encountered the stench himself.
"The air was still that night, and it was enough to make my eyes sting and water," he said.
Farmers and officials are constantly monitoring flocks for flu symptoms. Loss of appetite, lethargy and a drop in egg production point to infection in chickens. Afflicted turkeys develop a star-gazing look and twist their necks; death follows quickly.
And as new bird flu cases pop up — about 50 sites have been affected in Iowa — people across the state are beginning to question the quality of their food and whether the virus will be contained anytime soon.
"I wonder if I should, you know, be cooking these eggs for my daughter," said Jeanne Forsyth, a waitress at Anything Sweet & More Cafe in Winterset.
Forsyth, who used to work for Rose Acre Farms, says she is now debating whether she should start buying free-range eggs. Farmers of free-range chickens argue that their birds are less susceptible to the infection because they are healthier than chickens confined in cramped cages, which allow the diseases to pass easily from one bird to another.
"The more I think about it, I would like my daughter to eat healthy," Forsyth said.
State officials have stressed that the eggs currently sold in local markets are safe to eat and the risk of people contracting the virus is low.
The virus is spread by wild birds that leave their droppings on farms, said Iowa Agriculture Secretary Bill Northey.
"There could also be lateral movement," he said. "Little bits of the flu on dust or dander, or something walked in from a person's shoes from one facility to another."
And then there's the weather. Ultraviolet rays help kill off the influenza virus, according to the USDA, but Iowa has seen more thunderstorms and rain than sunshine lately.
Egg prices have gone up slightly as a result, Northey said.
Jeanne Pierce, a cashier at the Ben Franklin general store in Winterset, says her family goes through about a dozen eggs each week. Although she expects egg prices to "go sky-high," she says she's more concerned about the bird flu spreading to her children's farm just outside the quarantine zone imposed around Rose Acre Farms.
"It's scary to see those guys out there in their hazmat-like suits," Pierce said. "My kids have about 25 chickens. … I am worried about it."
In an effort to keep the virus from spreading, contaminated facilities are not allowed to move products without approval from the Iowa Department of Agriculture and Land Stewardship, Northey said.
"For us to say it's OK to move, we require a test to prove there's no bird flu on product," he said.
Disinfecting often means lots of bleach solutions applied to shoes, car and truck tires. Some farms have adopted a "shower in, shower out" policy for workers. And frequent hand-washing is a must too. After flocks are destroyed, workers disinfect the sprawling barns, a time-consuming process.
But can the flu be stopped? Iowans worry how far it will spread.
Northey said he ran into a turkey grower at a local grocery store who was "scared to death" of the outbreak and what it would mean for his animals. The man's wife said he stopped going to the convenience store, fearful he could touch something contaminated.
Some farmers with healthy flocks have even asked that the roads around them be blocked off — "to avoid getting the virus tracked in," Northey said. "They treat everything like it's hot."