You probably know someone who's staying at home for a week because her or his child has been come down with what is very likely "swine flu"--close enough to stay out of school, those breeding grounds of infectious diseases. I certainly do. Just last night much of dinner conversation was on this topic, and I came home to find an email that another friend would have to stay home for a work because her 13-year-old woke up with it yesterday morning.

The origins don't matter that much to my friend, just how long it will take her child to recover and how long she'll be home. But they matter, of course, to those in public health looking ahead. The link between the Smithfield processing plant in Vera Cruz, Mexico and the first human cases is fiercely disputed by Smithfield and the pork industry; and now leftist Web sites are trying to bring in possible origins at the Smithfield plant in Tar Heel, North Carolina, the world's largest slaughterhouse and the site of an affecting scene in Food, Inc.--something still extremely conjectural and sure to be yet more antagonistic to Smithfield and industry.

Pinpointing the origins are less important, Bill Niman and Nicolette Hahn Niman write, than the large and obvious underlying fact that factory farms are bad for animals, and provide easy breeding grounds for contagious illnesses and the "reassortments" of viruses we've been reading so much about. They also point out recent and un-reassuring evaluations of the origins and infection routes of recent outbreaks of bird flu--a source of current concern because of "reassortments" of mixed avian and swine flu strains.

Useful to recall that thorough cooking of meat rids it of most pathogens, and you can't catch swine flu from eating meat. Any meat. Go ahead and order pork if you like it! (Chicken, well...that's for another day, but not because of avian flu.) Also useful to recall that extremely close confinement isn't health-promoting for animals or, in my friends' neighborhoods lately, for schoolchildren.

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