Joanna Blythman

THE epicentre of the swine flu virus now spreading around the globe is an otherwise unremarkable village in the eastern state of Veracruz, Mexico. The only thing particular to La Gloria is that 12 miles out of town there is a vast intensive pig "facility" - even the corporation that owns it doesn't call it a farm - operated by Granjas Carroll, a subsidiary of the world's biggest pork producer, US giant, Smithfield.

An uncanny coincidence, or worse? Smithfield insists that it can find no clinical signs of the virus in either its livestock or its workers, but locals are adamant that the disease is linked to pollution from it operation. Alarmed by the spread of a strange respiratory disease which has now affected 60% of the population, La Gloria's residents have tried to get authorities to do something, efforts which, according to local accounts, merely led to the arrest of several community leaders and death threats against people speaking out against Smithfield.

Local health officials finally investigated in late 2008, embarrassed when a daily newspaper, La Jornada, printed an article about "the clouds of flies that come out of the hog barns and the waste lagoons into which this giant pig facilty spews tonnes of excrement", along with a photograph of a young boy holding a placard with a picture of a pig crossed out and the words, "Danger: Carroll's Farm".

Bear in mind that swine flu is a promiscuous cocktail of pig, bird and human influenza strains and that the region around La Gloria is also home to several large intensive poultry units. Last year, there was an avian flu outbreak on one such unit about 50 kilometres from La Gloria, owned by Mexico's largest poultry company, Granjas Bachoco. Campaigners believe that this outbreak was not revealed until recently because of fears that it might be bad for Mexico's food exports.

We can't know exactly what caused the genetic recombination that gave us a swine influenza capable of killing perfectly healthy humans, but the obvious place to start looking is in the intensive pig and poultry units of Mexico and the US. Let's not be slow learners here. Factory farms may be breeding grounds for global disease epidemics, and some people fear that swine fever is shaping up to be the global meat industry's latest pestilence.

Our relatively modern expectation of cheap and plentiful meat has spawned an ugly industry. It may represent "progress", if by that you mean churning out previously unprecedented volumes of cheap animal protein, but for livestock, factory farming represents the dark ages, turning sentient animals into expendable production machines. Now this model of meat production is said by some to threaten not only animal, but also human health.

In the 1980s, a "big" pig farm had 100 pigs. Now it has 5000 crammed into massive industrial indoor units. As a headline in the US trade journal National Hog Farmer put it: "Overcrowding pigs pays - if it's managed properly." Crowded and unsanitary conditions on factory farms incubate disease and encourage relatively harmless viruses to take on new forms. "Because they tend to concentrate large numbers of animals close together, they facilitate rapid transmission and mixing of viruses," the US National Institutes of Health has warned. Once this happens, the disease can spread far and wide in a matter of days, whether by breeding stock, faeces, feed, water or even on workers' boots. Today's globalised intensive meat trade is a vertically-integrated industry, where the same companies produce breeding stock, operate feed mills, own transport and slaughter facilities and are represented, or send their products, over national boundaries.

Swine flu has disturbing echoes of bird flu H5N1. Its epicentre was the intensive poultry farms of Asia. One theory is that H5N1 originated at Qinghai Lake in northern China which is surrounding by intensive poultry farms whose "poultry manure", a euphemism for what is scraped off the floor - bird faeces, feathers and soiled litter - was used as feed and fertiliser in fish farms and fields around the lake. Worldwide, intensive poultry production, like pig meat production, has exploded and this growth has been mirrored by an increase in avian flu. In southeast Asian countries, where most of the H5N1 outbreaks are concentrated - Thailand, Indonesia and Vietnam - production has jumped eight-fold in just three decades as cheap chicken meat has become an international commodity. Thai chicken, for instance, is a common ingredient in many UK ready-meals. They don't yet contain Mexican pork, but if our taste for cheap foreign meat persists, anything is possible.

As leaflets come tumbling through our doors alerting us to symptoms of swine fever, we should feel very angry indeed. The World Health Organisation's (WHO) global surveillance systems have ignored the time-bombs ticking away on the factory farm, and the WHO's response is not prevention, but cure - another Big Pharma solution to Big Food's dirty secrets.

No wonder share prices of drug companies producing vaccine are going through the roof. But sooner or later, our health authorities must start joining the dots. Factory farms are incubators for pandemics and will continue to be so until their expansion is stopped and put into reverse.