Editor’s Note: Tom Philpott’s April 28 piece on the swine flu pandemic, which raised the question of whether there is a link between the virus’ emergence in Mexico and the presence nearby of factory-scale pork farms, sparked a vigorous debate on the Society for Environmental Journalists listserv. Merritt Clifton was one of several writers to take issue with Tom’s piece. At Grist’s invitation, he put his critique into an essay form, which is posted below:

Thirty years ago this month I knelt beside the Yamaska River in southern Quebec with a test kit — downstream from several of the then-largest, factory-type pig farms in North America (which happened to lie upstream from the water intakes for the cities of Farnham and St. Hyacinthe) — and found that the Yamaska literally contained more extraneous chemicals from pig excrement than H2O.

The predictable happened as the weather warmed. By midsummer thousands of people were ill. My exposés helped to bring the construction of new water filtration and treatment plants–but did not slow the growth of factory farming. Three out of every five Quebec farmers sold out to the mega-conglomerates or were forced out of business during the next 10 years.

Twenty-three years ago this month I was the first volunteer firefighter to arrive at burning factory farrowing barn. Ten minutes ahead of the trucks with the equipment, I found no way to free any sows and piglets before all roasted alive in their steel farrowing crates, squealing in terror and agony.

As a lifelong second-generation vegetarian, and longtime vegan, I would like nothing more, for both humane and environmental reasons, than to see an end to factory farming.

Yet in exposing and attacking the many and often grotesquely obvious excesses of factory farms, I believe it is essential at all times to be fair, be accurate, and not amplify allegations which may be unsubstantiated–not least because amplifying an unfounded or premature allegation tends to erode the credibility of the critic.

As of the moment, about two weeks into formal medical forensic investigation, no one knows just what the source of the mutant H1N1 virus first discovered in the Vera Cruz region of Mexico might have been.

Much attention has been given to the case of five-year-old Edgar Hernandez, of the La Gloria hamlet in Perote, near the Granjas Carroll factory pig farm. Hernandez–who survived–is the earliest victim of the mutant H1N1 virus from whom a sample was preserved. La Gloria residents blamed Granjas Carroll for an outbreak of illness in February and March 2009. Officially attributed to biting flies, the illness produced flu-like symptoms.

Granjas Carroll is half-owned by Smithfield, the world’s largest factory pig producer, involved in pollution incidents at multiple sites on several continents. As the mutant H1N1 virus is a variant of an illness that is generically if somewhat inaccurately termed “swine flu,” one might be tempted to presume that this disease, often lethal in Mexico, has incubated and emerged as result of the intensely unnatural manner in which Smithfield raises pigs for slaughter.

Prudence dictates waiting for substantial medical evidence. Though the Hernandez sample is the oldest that exists, flu-like illnesses had already been reported throughout the region for weeks. Granjas Carroll, however, reported no unusual disease outbreaks among either pigs or staff. Biting insects associated with pig waste may have infected La Gloria residents with something, but many insect-borne illnesses produce flu-like symptoms, including the malarial and rickettsial disease families, which are of protozoan and bacterial rather than viral origin, and are known to occur in the vicinity.

There are reports that at least one migrant worker returned to La Gloria with a flu-like illness contracted in the U.S., and spread it, before Hernandez fell ill. The nature of influenza is that a new strain may be quite widely distributed before it turns deadly. Often the deadly turn comes in a place where environmental conditions, weather, or a population already weakened by some other disease produce unique susceptibility. La Gloria may be such a place, and the presence of the pig farm may be a factor.

Yet even this would be far from indicting the pig farm for the disease itself, which may have emerged thousands of miles away, and might as easily have arrived with the migrant worker as it appears to have spread outward from Mexico, once people started looking for it.

By then the mutant H1N1 virus might already have been distributed worldwide. But only in the right–or wrong–conditions would it behave differently enough from any other flu to be identified.

Perhaps the migrant worker, or some other person who was the actual Vector One, contracted the disease while working at a U.S. factory farm. Or perhaps Vector One wrapped sandwiches at a fast food restaurant, and picked up the various reassorted “swine flu” strains that comprise this new variant of H1N1 from co-workers who had other versions of common flus.

Until the medical evidence is in, we just don’t know. And focusing prematurely on the presumed factory-farm connection could prove a dangerous distraction from identifying and responding to the actual source of a potential pandemic.