PLAGUES HAVE GONE Hollywood, taking the place of nuclear conflagration as the most likely vehicle of human extinction. Christopher Wills, however, in his calm and complex overview of the history and possible future of plagues, argues that such fears are overblown. Plagues are bad, of course, but the power to prevent them lies squarely within our grasp.
Wills demonstrates that what humans experience as an acute crisis is often, in nature, little more than a temporary maladjustment of the smallest factors. This is especially true in the case of plagues. In our imagination, plague viruses are malevolent creatures, possessed with a will to destroy. In reality, plagues are deadly because the viruses and bacteria which cause them are so weak.
Alternating between scientific explanation and historical examples, Wills documents how nature and human society interact to allow plagues to spread. For instance, the bacterium that causes bubonic plague is crippled: Unlike most other bacteria, it can't swim or survive for long outside its host. He then shows how these features interacted with overcrowded, unsanitary social conditions to create the Black Death of 1348, which killed 40 million Europeans.
Of course, killing one's host is a poor way to ensure survival, so the most virulent bacteria and viruses tend to die out. Pathogenic strains emerge when ecological systems are disturbed; and since humans are constantly disturbing the ecological balance, Wills observes that plagues are not the anomalies we'd like to think, having "afflicted most species of animals and plants for most of the time that life has existed on our planet." So why are we still around? Partly, again, this is because pests that destroy their hosts tend to lose out in natural selection. Another reason is that the genetic diversity within all species, including humans, assures that at least some individuals are resistant to each evolving plague.
The long history of plagues indicates that the real threat to humans isn't a killer virus emerging from the depths of a rainforest somewhere. Although Wills is a biology professor, he finds that the menace of plagues stems more from politics then the environment. For instance, governments allowed AIDS to spread rapidly by ignoring or minimizing the disease, especially in Africa. And as the public health infrastructure deteriorates in the First World and fails to materialize in the Third World, we face a situation where plagues may become more common and take more lives. If we covered our bases in areas like sanitation, education, and basic medical care, then plagues, while inevitable, would take a very small toll in human life. But as Wills notes, finding the political determination to prevent plagues is usually more difficult than finding medical means to curb or cure them.