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At first glance, it looks like an unremarkable farm. Cows are scattered across fenced fields. In the distance, a milking parlor with a tractor next to it. But the people working there aren’t farmers, and other buildings look more like what you’d find at a modern university than a cow pasture.

Welcome to the National Animal Disease Center, a government research center in Iowa where 43 scientists are working with pigs, cows and other animals to address the bird flu outbreak currently spreading among America’s wildlife and develop ways to stop it.

Of particular importance is the testing of a vaccine for cows that is designed to stop the further spread of the virus, in the hope of reducing the risk of the virus ever becoming a widespread disease in humans.

The U.S. Department of Agriculture facility opened in 1961 in Ames, a college town about 45 minutes north of Des Moines. The center is located on a 523-acre (212-hectare) pastoral site a few miles east of low-lying downtown Ames.

It’s a quiet place with a rich history. Over the years, researchers there have developed vaccines for several diseases that threaten pigs and livestock, including swine fever and brucellosis. And work there during the 2009 H1N1 influenza pandemic — then known as “swine flu” — proved that the virus was confined to the respiratory tract of pigs and that pork was safe to eat.

The center has the unusual resources and experience to do this kind of work, said Richard Webby, a leading flu researcher at St. Jude Children’s Research Hospital in Memphis.

“That’s a capability that isn’t available in many places in the U.S.,” said Webby, who is working with the Ames facility on vaccinating cows.

The campus has 93 buildings, including a high-containment laboratory building that looks like a modern megachurch on the outside but is a series of compartmentalized hallways and rooms inside, some of which contain infected animals. That’s where scientists work with more dangerous pathogens, including the H5N1 bird flu. There’s also a three-story office building that houses animal disease researchers, as well as a testing center that’s an “animal-only” version of the CDC’s labs in Atlanta that identify rare (and sometimes scary) new human infections.

About 660 people work on campus, about a third of whom are assigned to the Animal Disease Center, which has an annual budget of $38 million. They were already busy with a wide range of projects, but became even busier this year after the H5N1 bird flu unexpectedly jumped to U.S. dairy cows.

“It’s just amazing how people just get on with it and make it work,” said Mark Ackermann, the center’s director.

First identified in 1959, the virus has become a widespread and highly lethal threat to migratory birds and domestic poultry. Meanwhile, the virus has evolved and in recent years has been found in a growing number of animals, ranging from dogs and cats to sea lions and polar bears.

Despite the spread in different animals, scientists were surprised this year when infections were suddenly discovered in cows — specifically in the udders and milk of dairy cows. It’s not unusual for bacteria to cause udder infections, but a flu virus?

“We normally think of influenza as a respiratory illness,” said Kaitlyn Sarlo Davila, a researcher at the Ames facility.

Much of the research into the disease was conducted at the U.S. Department of Agriculture’s poultry research center in Athens, Georgia. However, the presence of the virus in cows prompted the Ames center to become involved.

Amy Baker, a researcher who has won awards for her work on flu in pigs, is now testing a vaccine for cows. Preliminary results are expected soon, she said.

USDA spokesman Shilo Weir called the work promising, but still early in development. There is no approved avian flu vaccine used on U.S. poultry farms, and Weir said that while work is underway on poultry vaccines, such a strategy would be challenging and not guaranteed to eliminate the virus.

Baker and other researchers have also been working on studies trying to see how the virus spreads between cows. That work takes place in the high-containment building, where scientists and animal caretakers wear specialized ventilators and other protective equipment.

The study exposed four yearling heifers to a virus-carrying mist and then injected the virus into the teats and udders of two lactating cows. The first four cows became infected but showed few symptoms. The second two became more ill, with a loss of appetite, a decrease in milk production and thick, yellowish milk.

The conclusion that the virus spread primarily through exposure to milk with high levels of the virus — which could then spread via shared milking equipment or other means — was consistent with what health researchers understood was going on. But it was important to do the work, because it was sometimes difficult to get complete information from dairy farms, Webby said.

“We had at most a suspicion about how the virus was circulating, but we didn’t really know,” he added.

Scientists from the United States Department of Agriculture (USDA) are conducting further research and testing the blood of calves that have drunk raw milk for signs of infection.

A study by the Iowa center and several universities found that the virus had likely been circulating for months before it was officially reported in Texas in March.

The study also noted a new and rare combination of genes in the bird flu virus that jumped to the cows. According to Tavis Anderson, who co-led the study, researchers are still investigating whether this allowed the virus to spread to cows or between cows.

In any case, the researchers in Ames expect to be busy for years to come.

“Do they (cows) have their own unique influenzas? Can it go from a cow back to wild birds? Can it go from a cow to a human? From a cow to a pig?” Anderson added. “Understanding those dynamics, I think, is the key research question — or one of them.”

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Stobbe reported from New York.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Science and Educational Media Group. The AP is solely responsible for all content.