VERNALIS, Calif. -- Andrew Carlson cupped a day-old chick in his palm as a sea of 25,000 yellow fluff balls peeped and pecked around him.
Placing the chick on the ground, he checked automated food and temperature controls in the cavernous henhouse west of Modesto, then returned to his truck and unzipped his full-body biosecurity suit.
Instinctively, Carlson reached for a bottle in the door pocket, squirted a dollop of clear gel into his calloused hand and rubbed it in.
''Farmers using hand sanitizers," he said. ''Crazy, huh?"
In the age of bird flu, the ideal poultry or egg farm would be more controlled than a prison, more sanitary than a hospital, and more remote than a desert island.
Reality is not far off. The new tools of the trade are locked gates, visitor logs, and antiviral truck washes. Failure to wear biosecurity gear is a firing offense.
A single diseased bird milling around a crowded poultry barn or sneezing inside a cage at a large egg farm could set off a chain reaction that wipes out millions of others.
It has happened in Asia, where more than 120 million birds have died or been culled because of the spread of the H5N1 avian influenza virus. Now, the virus has spread to Europe and Siberia, and US farmers are bracing for the possibility that it will arrive in North America.
Carlson, 25, and his wife, Theresa, pregnant with their first child, live on the farm he grew up on in a tiny red house that belonged to his late grandfather.
He keeps his grandfather's hours, rising by 3:30 a.m. and returning home at 6:30 p.m. or later. In most other ways, his grandfather wouldn't recognize Carlson's approach to chicken farming.
He majored in law and society at the University of California at Santa Barbara, and studied macroeconomics at Lund University in Sweden to understand global agriculture.
When he returned as his company's chief operating officer three years ago, Carlson realized that his studies neglected the key topic in modern poultry and egg farming: biology.
''When you grow up on a ranch, you know about predators, coyotes and such. But I didn't imagine the main predator would be like this," he said, indicating a microscopic speck between thumb and forefinger. ''A virus."
Since 2002, Carlson has tripled his spending on biosecurity to more than $100,000 per year. Such costs are one reason most small bird farms have been replaced with efficient and secure chicken-growing factories.
Bird flu has ravaged farms throughout Asia, and international health officials are worried that the virus could mutate into a form passed easily among humans, sparking a pandemic. As of Friday, 141 people have caught the disease, according to the World Health Organization. Nearly all the victims, including 73 who died, had close contact with sick birds.
Many American farmers blame the severity of bird flu in places such as Vietnam on the common intermingling of sick birds, pigs, and people on backyard farms. They regard the risk here of the virus jumping from farm to farm -- or from birds to people -- as remote.
''We don't live with our chickens," said Kim Hernandez of Haley Farms, a fryer producer in Modesto.