An earlier post considered the accuracy of the term “swine flu” and its misleading suggestion of a clear and direct link between human cases of the new strain of the influenza virus and pigs.
There’s currently no scientific certainty about the source of the new Mexican strain of H1N1 flu, nor even any evidence of the virus circulating in pigs or that it could infect pigs, but circumstantial evidence is emerging that should direct epidemiological investigations.
Searching for patient zero
Crucial to identifying the source of the virus is pin-pointing the first human sufferer. “Patient zero” was first thought to have been a woman from Oaxaca, admitted to hospital on 8th April with suspected pneumonia, but subsequently confirmed as the first known case of the new virus. Oaxaca is not a pig-producing area and the woman appears to have had no contact with pigs.
However, a new patient zero has emerged more recently: a four year-old boy, from the village of La Gloria in the province of Veracruz, who is now confirmed to have contracted the new strain 2 weeks previously (happily he recovered, though at least 2 infants died from similar symptoms, but are as yet unconfirmed as new flu strain).
The La Gloria case presents closer circumstantial links with pigs, as Veracruz is a major pig-producing area, with a large industrial pig production operation 12 miles from the village.
Examining the circumstantial evidence
While the mainstream media concentrated on the spread and pandemic potential of the new virus, bloggers were the first to investigate and question the circumstantial suggestions that the new strain may have emerged from intensive pig production units, or CAFOs (confined animal feeding operations).
Edmund Harris of the UK’s Local Foods Research blog has summarised early reports – by Tom Philpott at Grist, Paula Crossfield at Civil Eats and Paula Hay at Peak Oil Entrepreneur – of the possible link between the outbreak and the pig production facilities of Granjas Carroll, a Mexican subsidiary of Smithfield Foods, the world’s largest pig producer. (Local Foods Research has a later update and photos of the Granjas Carroll site at La Gloria.)
Unsurprisingly, Smithfield has rejected these suggestions, asserting that:
it has found no clinical signs or symptoms of the presence of swine influenza in the company’s swine herd or its employees at its joint ventures in Mexico
Meanwhile, over at Fair Food Fight, hardly a friend of big agri-business, El Dragón is disappointed by the weakness of Tom Philpott’s arguments, particularly the reliance on dubious sources.
Questions but no certainty
There are important questions to ask about the source of the virus but it’s important to keep in mind the essential difference between circumstance and epidemiology.
There simply isn’t any current scientific certainty about the source of virus, though circumstantial evidence should help in directing epidemiological investigations.
The speed of bloggers to raise pertinent questions about the possible source of the new strain is admirable. They may have missed some important scientific distinctions (eg between viruses and bacteria), made unscientific inferences from admittedly unpleasant aspects of the production units (eg flies), presented the only available sources (ie locals) as more reliable than they truly are, and been over-hasty in asserting their conclusions; but this is no different from the mainstream media, which has since rushed to ask the same questions and repeated many of the same mistakes.
A Times headline today proclaims: “Mexico outbreak traced to ‘manure lagoons’ at pig farm”. No, not yet anyhow.
How risky is industrial livestock production?
The Huffington Post has reported on the wider risk from industrial livestock production of emergent new viruses and pathogens, citing the Pew Commission on Industrial Farm Animal Production’s apparently prescient warning:
The continual cycling of swine influenza viruses and other animal pathogens in large herds or flocks provides increased opportunity for the generation of novel viruses through mutation or recombinant events that could result in more efficient human-to-human transmission of these viruses. In addition, agricultural workers serve as a bridging population between their communities and the animals in large confinement facilities. This bridging increases the risk of novel virus generation in that human viruses may enter the herds or flocks and adapt to the animals.
While the development of industrial farming methods over the past 50 years has coincided with a period of relatively limited pandemic activity, there are worrying indications that we’re running a high risk and just may have finally run out of luck.
Only rigourous science can conclusively answer these questions – and provide hope of containing the outbreak.
