Factory farming refers to the industrialized method of raising animals to be eaten food. Factory farming is referred to by the Environmental Protection Agency and the Centers for Disease Control as "concentrated animal feeding operations (CAFOs)."Centers for Disease Control: Concentrated Animal Feeding Operations (CAFOs)
Factory farms keep the animals confined to small areas and many scientists have expressed concern that such farms could provide breeding grounds for new pathogens that could infect the human population. In late-April 2009, some reports suggested that the swine flu could have originated at the Smithfield factory farm in Mexico.USNews.com: Swine Flu and Factory Farming (April 28, 2009)