A swelling number of scientists believe swine flu has not happened by accident. No: they argue that [it] is the direct result of our demand for cheap meat. So is the way we produce our food really making us sick as a pig? The scientific evidence increasingly suggests that we have unwittingly invented an artificial way to accelerate the evolution of these deadly viruses - and pump them out across the world. They are called factory farms. They manufacture low-cost flesh, with a side-dish of viruses to go. In most swine farms today, 6,000 pigs are crammed snout-to-snout in tiny cages where they can barely move, and are fed for life on an artificial pulp, while living on top of cess-pools of their own stale faeces. The virus ... has a pool of thousands [of pigs], constantly infecting and reinfecting each other. The virus can combine and recombine again and again. The ammonium from the waste they live above burns the pigs' respiratory tracts, making it easier yet for viruses to enter them. Better still, the pigs' immune systems are in free-fall. They are stressed, depressed, and permanently in panic, making them far easier to infect. There is no fresh air or sunlight to bolster their natural powers of resistance. They live in air thick with viral loads, and they are exposed every time they breathe in. As Dr Michael Greger, director of Public Health and Animal Agriculture at the Humane Society of the United States, explains: "Put all this together, and you have a perfect storm environment for these super-strains. If you wanted to create global pandemics, you'd build as many of these factory farms as possible."