The high-grade form of anthrax in a letter sent to Sen. Tom Daschle may be the work of the Al Qaeda network, or it may have come from some other source. But either way, it has forced authorities to a sharp conclusion: The perpetrators are much more sophisticated than many originally believed.
The key here is particle size. The anthrax found in Senator Daschle's office was fine enough that it could float easily through the air, rather than simply falling to the ground. At least 31 people have already tested positive for exposure in Senate offices. In a chaotic morning yesterday, the US House of Representatives planned to shut down until next Tuesday, after a full sweep of the premises.
There are still many obstacles to carrying out an anthrax attack with, say, a crop-duster - such as getting hold of the right equipment, and overcoming weather conditions. But the ability to manufacture fine particles puts the terrorists one step closer to achieving that goal.
As a result, the United States is in what a number of experts have called a technological "race" - with terrorists closing in on better methods of production and dissemination of biological weapons, and the US government trying quickly to develop technology that could prevent such an attack.
"We are in a race with the terrorists to prevent them from getting the delivery system for biological and chemical weapons, and to stop them before they acquire nuclear waste, radioactive material, or heaven forbid, a nuclear device," says Rep. Christopher Shays (R), chairman of a House subcommittee on national security. "That's what this is about."
Some sources suggest that, in sending anthrax through the mail on a limited basis, the terrorists may be conducting a sort of test - to see how the system responds, before they launch a bigger attack. On the other hand, they may just send a flood of letters - yesterday, New York Gov. George Pataki's office also tested positive for anthrax exposure and was closed.
Others worry that the anthrax episodes may simply be a deliberate distraction, diverting attention from a completely different kind of attack, such as a smallpox release. "It can become a distraction for a greater threat," says Representative Shays.
But even if no larger sort of attack is in the works, the highly refined anthrax found in Daschle's office is cause for concern, say experts, because it means it's much more likely to be lethal. Health experts say inhalation anthrax, which occurs when particles get lodged in the lungs, is far more dangerous than cutaneous anthrax, which is transmitted through the skin.
"The main source of worry is how refined [the anthrax] is, and the particle size being very small," says Leslie-Anne Levy, a research associate at the Henry L. Stimson Center in Washington.
"To aerosolize a biological agent requires a very small particle size that can actually hang in the air.... That's something that's pretty difficult to do."
More troubling, the difficulty of manufacturing such a high-grade sample is leading some experts to believe it may in fact be a case of state-sponsored terrorism.
"The likelihood of state sponsorship goes up with the purity of the strain," says Raymond Tanter, a Mideast expert. "And the inference is, only Iraq and Iran could be the culprit - and Iraq seems to be the top candidate."
As of this writing, members of the Senate, while favoring environmental checks, were arguing on the side of not leaving unless absolutely necessary.
"The reaction in the House has been a little bit excessive," says Sen. John Kerry (D) of Massachusetts. "There is no scientific evidence at this point in time to not stay and do our work."
Pointing out that the number of letters containing anthrax is still extremely small, Senator Kerry adds, "This is not an epidemic. This is a blunt instrument to scare people into not doing their jobs."
Staff writers Francine Kiefer and Gail Russell Chaddock contributed to this report.