The Human-Animal Link

IN RECENT YEARS, outbreaks of diseases such as avian flu, severe acute respiratory syndrome (SARS), the Ebola virus, and mad cow disease have frightened the public, disrupted global commerce, caused massive economic losses, and jeopardized diplomatic relations. These diseases have also shared a worrisome key characteristic: the ability to cross the Darwinian divide between animals and people. None of these illnesses depends on human hosts for its survival; as a result, they all persist today, far beyond the reach of medical intervention. Meanwhile, humanity has become vulnerable to cross-species illnesses, thanks to modern advances such as the rapid transportation of both goods and people, increasing population density around the globe, and a growing dependence on intensified livestock production for food. The global transport of animals and animal products, which includes hundreds of species of wildlife, also provides safe passage for the harmful bacteria, viruses, and fungi they carry, not to mention the prion proteins that cause insidious illnesses such as mad cow disease and chronic wasting disease in deer and elk. Adding to the risks is the fact thgt while many people in the developed world would scarcely recognize meat if it did not come wrapped in clear plastic, the vast majority of people on the planet today still slaughter animals for meat themselves or buy it fresh, salted, or smoked in open-air markets. These markets generally go