British scientists question U.S. estimate of risk of smallpox.(Chicago Tribune)

CHICAGO _ As the U.S. government rushes to buy enough smallpox vaccine for every American, experts disagree about how to meet a potential bioterrorist threat posed by a deadly disease that officially has been eradicated worldwide since 1979.

In the latest edition of the journal Nature released this week, British scientists published a computer model that estimates that once an outbreak occurs, smallpox could spread through a population faster than previously thought.

The British study's estimated rate of secondary infections is at least twice the predicted rate in another computer model released recently by the Atlanta-based Centers for Disease Control and Prevention.

The debate over how fast the disease would spread highlights a growing list of uncertainties about smallpox that scientists are scrambling to understand.

The dangers of smallpox to a modern industrialized nation are basically untested. The virus no longer exists in …