NATURAL EPIDEMICS ARE scary enough. Today, however, people have come to fear a type of disaster that in some ways seems even worse: an epidemic caused by bacteria or viruses that either escape accidentally from a laboratory or are unleashed deliberately as an act of warfare or terrorism. Small-scale incidents of these kinds have already happened, and many experts think that larger ones may soon follow.

Close brushes with disaster

Individuals have certainly died from epidemic diseases accidentally acquired from laboratories. For instance, the last recorded death from smallpox took place in 1978, after the disease had been eradicated in nature. At that time, stocks of the smallpox virus were kept at several laboratories in different parts of the world. The virus somehow escaped from a laboratory at the University of Birmingham in Britain and fatally infected Janet Parker...