In the past five years, the bird flu epidemic claimed 186 victims worldwide. In the same period, another less-recognized but growing menace maimed or killed millions of people and produced massive economic losses. Like others, this dangerous pandemic ignores national borders and erupts in different places at different times. Inexplicably, it has surged in Boston and abated in Bogotá. Experts disagree about its precise causes and what explains its sudden eruptions. Unlike bird flu, it is not caused by a virus transmitted from one species to another; it is exclusively created and spread by people. I am talking about street crime.

The world is experiencing a crime pandemic. Crime rates are on the rise almost everywhere, and these statistics typically are distinct from the death and mayhem that comes with terrorism, civil war, or major conflict. The data reflect the booming number of civilians assaulted, robbed, or murdered by other civilians who live in the same city, often in the same neighborhood. Frequently, the victims are as poor as the criminals.

Crime has increased steadily for all the countries the United Nations measures, according to a 2003 U.N. report. Even in the United States, where crime rates famously declined since the mid-1990s, violent crime has risen sharply in the past two years. In 2005, violent crime had its largest annual increase in 15 years. The Police Executive Research Forum, a U.S. law enforcement association, reports that homicides increased in 71 percent of the American cities that were surveyed, robberies increased in 80 percent of them, and aggravated assaults with guns increased in 67 percent between 2004 and 2006. In Boston, murder rates are at an 11-year high. Crime is also a major problem in Britain; the European Union (EU) calls it a “high crime country.”

Of course, the United States and Europe are still...