Where do swine flu, avian flu and potential influenza viruses of the future find a rich breeding ground? In the production sites of industrial agriculture, some disease experts say.

Industrial poultry and swine production can foster the mixing of flu viruses such as the new influenza A (H1N1) strain, commonly called swine flu, which has components of human, bird and pig viruses.

Disease experts are starting to see links between conditions in industrial food animal production and public health, but the risks are not well measured, said Dr. Ann Marie Kimball, professor of epidemiology at the University of Washington's School of Public Health and a specialist in emerging diseases.

ALEXANDRE MENEGHINI / ASSOCIATED PRESS>

Pigs on a farm in Mexico's Veracruz state.

Kimball was among a panel of Seattle experts speaking at the University of Washington on swine flu Monday evening as part of the Washington Global Health Alliance Discovery series. TVW will televise the panel at 8 p.m. tomorrow.

Kimball said the globalization of travel, trade and extended chains of food production all represent risks for influenza as animals and people are transported across borders more than ever before.

She pointed out that people won't catch swine flu by eating pork or traveling on planes. With modern filtration systems in airplane cabins, people are unlikely to contract a virus through the air unless they're sitting next to a person coughing or sneezing.

Yet air transportation has played a central role in global transmission, since travelers exposed to viruses can carry them within hours to other countries.

Kimball said influenza surveillance may be missing the "sentinel populations" working close to animals, such as farmers, veterinarians and meat packers, particularly in places like Iowa where much of the country's pork is produced.

A report by the Pew Commission on Industrial Farm Animal Production found chronic overuse of antibiotics in animals and other problems with industrial farming has led to antibiotic resistance and become a threat to public health. More interesting commentary on that is here.

Commercial agriculture has experienced a boom in China, and most of it of takes place in urban areas, said Kimball, who directs the APEC Emerging Infections Network.

Just as avian influenza (H5N1) and SARS had connections to human contact with animals, reports in the Mexican press and elsewhere point to an influenza epicenter around a huge hog farm in Veracruz.

Around the world, global defenses are uneven, with poor and middle-income countries lacking enough resources to monitor and respond to a pandemic.

"You don't worry about countries reporting cases," she said. "You worry about countries that are very silent."