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Has the way we raise hogs helped create the swine flu variant that is now spreading across the globe? Mike Davis, in a column in the Guardian [2], writes that "corporate industrialisation of livestock production" in China and now across the world has transformed animal husbandry "into something that more closely resembles the petrochemical industry than the happy family farm depicted in school readers." He quotes a report from the Pew Research Center last year warning that industrial animal production causes a continual cycling of viruses that "increase opportunities for the generation of novel virus through mutation or recombinant events that could result in a more efficient human to human transmission."
Davis' column is based on a warning that appeared in a March 2003 article in Science magazine [3]. Bernice Wuethrich wrote that "after years of stability, the North American swine flue virus has jumped onto an evolutionary fast track, churning out variants every year. Changes in animal husbandry, including increased vaccination, may be spurring this evolutionary surge. And researchers say that the resulting slew of dramatically different swine flue viruses could spell danger for humans, too. The evolving swine flue 'increases the likelihood that a novel virus will arise that is transmissible among humans,' says Richard Webby, a molecular virologist at St. Jude Children's Research Hospital in Memphis, Tennessee."
Pigs are good "mixing vessels" where human, bird and hog viruses can swirl and match, producing new and sometimes deadly strains. The last two flu pandemics occurred when avian and human flu viruses swapped genes in pigs.