[Below is the original script. Some changes may have been made during the recording of this audio podcast.]

Amidst the hubbub surrounding the current pandemic threat from swine flu, an epidemiological mystery has been unfolding. Authorities have designated Edgar Hernandez, a five-year-old from La Gloria in the Mexican state of Veracruz as "Patient Zero"—at least he is the earliest case they have found so far. Virologists have determined that the mutating flu is a combination of several older flu strains, commonly associated with pigs. And La Gloria is home to nearly a million pigs on a nearby factory farm.

So is so-called swine flu really just another environmental problem associated with factory farming?

After all, such large operations keep the animals in close confinement, dope them with antibiotics to keep them alive in the crowded conditions and create vast pools and piles of waste—all good ways to promote the spread of any disease.

Other health threats, such as antibiotic-resistant strains of staphylococcus aureus, have emerged from pig farms as well.

Nevertheless, this H1N1 strain has not yet been found in the pigs near La Gloria, nor is it clear how it would have jumped from the factory farm to little Edgar.

But what is clear thanks to the hard work of virologists is that this particular strain of flu got its genetic start on U.S. hog farms back in the 1990s. That's according to the U.S. Centers for Disease Control. How the virus jumped from pigs to humans may have nothing to do with factory farms, but confined animal feeding operations helped to breed the disease.

—David Biello