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Potent Anthrax Means Expert Bioterrorists, Officials Say

Investigators still don't know where it came from, but the anthrax that killed two Washington postal workers seems to have the hallmarks of a sophisticated weapon built by someone who knows how to deliver a lethal blow. CBS's Bob Orr reports.

Microbiologist Richard Spertzel, who helped the United Nations track chemical and biological weapons in Iraq, says a microscopic amount of anthrax can kill if it's carefully refined and becomes airborne.

"Somebody knew exactly what they were doing," says Spertzel. "If the concentration of the material in the air were sufficient, certainly one breath would be enough."

Although there is little research on the effects of anthrax on people, microbiologists agree a dosage of 8,000 to 10,000 spores can be fatal if inhaled.

"You speak of 8,000 to 10,000 spores, but you have to understand that these are not apple-sized. So the quantity inhaled--you would never know," Spertzel says. Eight thousand to 10,000 spores are probably less than a speck of dust in the air.

Finely ground anthrax, when whipped into the air, is virtually invisible. Each spore can be no bigger than 5 microns--about a tenth as wide as a human hair--if it is to infect a person's lungs. Larger spores can be harmlessly trapped in nasal passages.

That appears to be what happened on Capitol Hill. More than two dozen staffers tested positive for exposure, but not infection, after the anthrax-laced letter was opened in Senator Daschle's office.

Again, microbiologists say the Capitol Hill anthrax appears to have been produced by a professional.

"The fact that 31 or 33 humans had spores in their nose following the opening of an envelope suggests that the material was pretty well done," says bioterrorist expert David Franz.

The potency of the anthrax has experts worried about what could happen next. They warn that any person or organization capable of producing this anthrax may be able to produce a more lethal biological weapon.

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