The U.S. government has known since the early 1990s about Soviet-era smallpox weapons, and collected circumstantial evidence of programs elsewhere.

For political and bureaucratic reasons, governments at all levels are telling far less to the public than to insiders about how to prepare for and behave in the initial chaos of a mass-casualty event.

The CIA now assesses that four nations - Iraq, North Korea, Russia and, to the surprise of some specialists, France - have undeclared samples of the smallpox virus.

Barton Gellman Quotes