Thanks to breakthroughs in production and food science, agribusiness has been able to devise new ways to grow more food and get it more places more quickly. There is no shortage of news items on hundreds of thousands of hybrid poultry - each animal genetically identical to the next - packed together in megabarns, grown out in a matter of months, then slaughtered, processed and shipped to the other side of the globe. Less well known are the deadly pathogens mutating in, and emerging out of, these specialized agro-environments. In fact, many of the most dangerous new diseases in humans can be...