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Swine flu source? Raising pigs in factory farms may have led to the current flu outbreak.

RODALE NEWS, EMMAUS, PA—The swine flu is spreading in the United States, with hundreds of students in New York City alone likely sickened from the new virus. In California, the Los Angeles Times reports that a coroner is looking into the deaths of two men, ages 33 and 45, who may have succumbed to the flu strain. On Tuesday, several people across the country were hospitalized for possible swine flu, though most cases so far have been mild. So where did this all start? It’s too early in the outbreak to be sure, but one possibility is that the filthy conditions, tight confinement, and huge number of animals housed inside buildings in concentrated animal feeding operations (CAFOs) present a perfect breeding ground for this type of viral manifestation. “It’s the likely scenario,” says Bob Martin, senior officer at the Pew Environment Group and executive director of the Pew Commission on Industrial Farm Animal Production, which released a 2-year independent study in 2008. Long before this outbreak, his group’s research pointed to serious concerns about commercial swine operations because of the role pigs play as conduits for swine and avian flu.

THE DETAILS: According to reporting by the Associated Press and other news outlets, the epicenter of the swine flu outbreak may be La Gloria, Mexico, where a 4-year-old boy fell ill with respiratory problems and tested positive for swine flu. (He recovered.) More than 400 hundred cases since have been reported in La Gloria, though the World Health Organization has confirmed only 26 cases, including 7 deaths. Residents of the small town blame hog CAFOs partially owned by Smithfield, Inc., an American company based in Virginia. Smithfield and the Mexican government deny the charges. However the story turns out, it’s a reminder of the unintended and unhealthy consequences of CAFO-style food production, says Ellen Silbergeld, PhD, professor of environmental health engineering at Johns Hopkins University in Baltimore, and editor-in-chief of the journal Environmental Research. “We need to start paying serious attention to the way in which we raise food animals, and the potential risks associated,” she says.

Crowding thousands of pigs or other animals into factory farms is like conducting a germ breeding program. “By raising animals within these highly confined spaces, we are driving the evolution of pathogens,” Silbergeld explains. “Every time a pathogen swaps a host and moves from one organism—a pig, a chicken, or us—to another, it’s an opportunity for that pathogen to mutate, acquire new genes, and change itself.” Not only do germs proliferate among the animals, they also can infect CAFO workers and be carried by flies.