It may be crowded and carpeted in manure, but the long white building beside State Route 38 is one of the most pathogen-free homes a pig could have.
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The animals don't know the feel of grass, mud or sunshine, and hardly the touch of man, in their six months of life. But they are also free of many of the infections that slow the growth and occasionally end the lives of their outdoor cousins.
"We're producing the most efficient animal, one that is healthy every day," said Devon Schott, the 34-year-old farmer who owns the building. To do that, he said, "biosecurity is of utmost importance."
Despite the buttoned-up methods of farmers such as Schott, many experts think pig farming presents a serious and overlooked risk to public health. Proof of that assertion — indirect but indisputable, in the opinion of virologists — is the 2009 H1N1 pandemic influenza.
Little is known about the origin of the novel H1N1. But one thing is virtually certain: The bug now infecting the people of more than 190 countries began in a pig.
A major concern now is what might happen if the pandemic H1N1 virus spreads widely in pigs, and then out again into the human population.
"We really need to know more about what is happening in the pig population in the United States," said Robert Webster, a leading avian influenza virologist. Scientists at the University of Minnesota and the University of Iowa revealed last month that they had identified the H1N1 strain in seven pigs at the Minnesota State Fair in late summer as part of a study of virus exchange between swine and people.
What worries virologists is the mixing of human and swine flu strains — or, worse, human, swine and bird strains. That can lead to "reassortment," in which strands of genetic material are exchanged to yield a new virus, often with behavior not seen in its parents. Those features can include higher contagiousness, rapid growth, the ability to infect the lungs and, most important, an unfamiliar appearance to the immune system.
Reassortment is rare, and it's even rarer when the product is a strain that can spread like wildfire.
A major goal of public health is to make such events even more rare. One way is to keep pigs and humans away from each other's flu viruses. It's been clear for a while, however, that there's a small but steady traffic of virus between America's 110 million pigs and the 120,000 people who care for them.
Influenza is transmitted from pig to human the same way it is transmitted from human to human — in respiratory droplets and in hand-to-mouth contact. Most cross-species infections end on the farm because swine flu strains, even if occasionally acquired by animal handlers, are almost never well-adapted to human hosts.
But there have been some close calls. One occurred in 2006, when the U.S. Department of Agriculture lab in Ames, Iowa, got samples from two farms in Missouri where pigs were ill.
The virus was a reassortment between a swine flu strain and avian flu strains found in mallard ducks and blue-winged teal. Both farms got water for the pigs from outdoor ponds, which scientists theorize contained flu virus from wild ducks.
More important, the H protein on its surface, which determines its transmissibility, was perfectly adapted to humans.
"We had good luck that this did not take ahold, and did not jump into humans," recalled Juergen Richt, a microbiologist at Kansas State University who was working in the Ames lab at the time.
It is to prevent such encounters that operations like Devon Schott's are a kind of down-on-the-farm version of "Hot Zone" laboratories.
Anyone entering his $525,000 metal building must shower and dress in coveralls and boots. That clothing and the towels — like the pigs — never go outside.
All 2,400 pigs come from the same source, arriving as 7-pound weanlings and departing five months later as 250-pound market hogs. They have about 8 square feet of space apiece and can eat and drink as much as they like.
Trucks deliver 23 tons of feed to three conical silos outside the barn. The food enters the barn on an automatic conveyer.
The purpose of such "confined animal feeding operations," or CAFOs, is to maximize fast and healthy growth. Gone are many of the things that once stood in the way — hog lice, mange, roundworms, hookworms and whipworms.
"We have eliminated or minimized so many diseases that used to be standard and common in the swine industry," said Mike Male, 57, a veterinarian who provides the medical care to Schott's animals. Influenza, however, isn't one of them.
Still, CAFOs are inherently safer than backyard pig farms, where the animals mingle with people and birds fly overhead. But if multiple flu viruses were to get into a CAFO, the crowding of the animals would make the chance of reassortment more likely.
"The thing we're concerned about is if this [H1N1] virus gets into pigs and then comes back out of pigs into people," said Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. "The question is what may happen to the genetics during the time it's in pigs."
The importance of keeping a human pandemic flu strain out of pigs is underappreciated, according to many experts.
Most American pig farmers — who have been losing money since the fourth quarter of 2007 — don't want to know whether the new strain is in their herds. Twenty-seven countries banned imports of U.S. pork last spring after the new virus was discovered in people — even though it wasn't in pigs and, in any case, flu can't be contracted from pork.
"People are really scared if their farm is the first one to find an outbreak of pandemic H1N1," said Richt, the microbiologist from Kansas State. "They are afraid they will lose their livelihood."
