Worse than any combination of natural disasters in the past 2,000 years, plague is the biggest modern killer of humans. It wiped out 40 percent of Europe's population in the Middle Ages, and early in the 20th century, it killed 12 million people in India alone. In Plague, Orent charts the history of the disease's major pandemics, detailing how each outbreak started, spread, and subsided. While science all but eradicated natural plague, genetically altered strains of its infectious agent still exist. Orent interviewed two Russian scientists who report that before the collapse of the Soviet Union, they developed vaccine-resistant strains of plague as potential weapons. These strains would be particularly lethal if unleashed because they would spread by person-to-person contact--as did the worst of past plague epidemics, Orent contends. Free Pr, 2004, b&w photos, 276 p., hardcover, $25.00.