EDITORIAL OBSERVER

In Sizing Up Anthrax, Don't Trust Your Gut

By PHILIP M. BOFFEY

If the anthrax crisis has taught us anything, it is that neither we -- nor the nation's supposed experts in disease and bioterrorism -- should trust our instincts or our presumed knowledge. That first became obvious as public health experts struggled to unravel the medical side of this unfolding mystery, only to find that much of what they thought they knew about the disease was probably not true. Now it looks as if bioterrorism experts may have been equally off base in their assumptions about who might have the skills, materials and motivation to carry out an anthrax attack through the mails.

The litany of public health misjudgments is well known but worth repeating as a reminder. When anthrax first struck, health authorities assumed wrongly that the only people in danger were those who opened an envelope containing anthrax, and perhaps others in the immediate vicinity. Tragically, it turned out that the tiny anthrax spores could readily escape through the pores of an envelope as it passed through postal machinery, and the primary victims were postal workers.

Health officials blundered next in assuming that ordinary letters that had simply touched intentionally poisoned letters or contaminated postal machinery could not become contaminated enough themselves to pose a hazard. That assumption has now been discarded and such incidental mail contamination is a prime suspect in the deaths of a 94-year-old woman in Connecticut and a 61-year-old woman in New York. Health officials have come to believe that some people, particularly the elderly, may succumb to far fewer spores than the 8,000 or more once deemed necessary for infection. Indeed, at least one germ warfare expert has suggested that a single spore might do it.

Those misfires make many people wonder how much stock to put in the latest assurance from health officials that the danger of infection from mail is slight even though tens of thousands of letters may have been contaminated as they passed through the postal system. The experts are probably right, given that the anthrax mailings occurred two months ago and we have seen no new cases of anthrax lately. Yet it seems impossible to rule out that somewhere a contaminated letter may still cross the path of a highly susceptible person, with tragic consequences.

The extreme volatility of this anthrax -- its ability to rise into the air after settling on an envelope or other surface -- has been a major surprise. For decades it has been dogma among germ warfare experts that anthrax spores, once settled, would not rise again in enough numbers to be harmful. Indeed, the premier scientific article on anthrax as a biological weapon, published in the Journal of the American Medical Association in 1999, suggested that there would be no need to clean an urban area or building after anthrax had settled on it. Yet the anthrax in the mailings is so volatile that it is hard to weigh on a scale, has spread readily to some 20 postal facilities in several states and has contaminated all three floors of a media building in Florida. Today, no one talks of leaving it in place. Offices are scrubbed and fumigated before they are deemed safe enough to enter.

Notions as to who might be conducting the anthrax attacks have also shifted repeatedly. When the first anthrax mailings occurred in early October, a nation already reeling from the Sept. 11 attacks naturally suspected this might be another assault by the same foreign terrorist network. But as time passed, federal investigators came to suspect it was the work of a domestic terrorist, perhaps a loner trained in biochemistry. Now, in the latest twist, some investigators suspect the perpetrator may have had ties to the American military, thereby obtaining access to either the anthrax itself or the knowledge of how to make it.

As reported in The Times this week by William J. Broad, preliminary analyses have found an extraordinarily high concentration of spores in the anthrax mailings, equal to the anthrax concentrations produced by the American military before it abandoned germ weapons and far more concentrated than any anthrax known to be produced by other governments. Further evidence on the origins of the anthrax may be provided by an analysis that got started this week of the material contained in a poisoned letter sent to Senator Patrick Leahy.