The inch-by-inch search of the American Media building in Boca Raton, Florida has continued, but has failed to produce any more evidence of anthrax contamination. The FBI remains convinced however that the outbreak was deliberate, though not terrorist-related.
"This thing in Florida truly is not an isolated event. Somebody did something that was criminal," Mr Mohamad Akhter of the American Public Health Association told a Senate hearing on Tuesday afternoon.
CNN yesterday reported that preliminary tests had linked the anthrax strain found to anthrax produced in an unspecified Iowa lab in the 1950s, although local health sources stressed that such findings were too preliminary to be reliable.
Whatever the source of the anthrax spores, the doctor of Robert Stevens, the man who died on Friday, said he received a huge dose, adding to the belief that he may have received a package or letter at his desk.
"The first look at his spinal fluid was overwhelming," said Dr Larry Bush. "There was a large amount of bacteria in the spinal fluid, which is never a good sign. It is a sign of overwhelming infection."
In Covington, Kentucky on Tuesday an Internal Revenue Service centre was shut for several hours and seven workers were treated as a precaution after a powder was found in the mail room, police said. An envelope containing the powder was removed for study.
Nervousness even spread to Canada, where a building in Montreal was briefly evacuated after employees of Globe International Inc, a company with close ties to AMI, noticed an envelope mailed from the Florida publisher.
In the last two days disturbed individuals have closed down a large part of the Washington metro system and caused a flight to be brought in to Chicago under fighter escort. In Kentucky last week six passengers died on an overnight Greyhound bus journey after a Croatian national cut the throat of the driver.
There is no doubt that in part acute public nervousness in the wake of September 11th has given a chilling new significance to incidents like these and the Florida inquiry.
But there is in many of them apparently a link, whether copy-cat or simply inspiration, to September 11th.
When Edward Coburn, a mentally deranged 31-year-old man, crashed through the door of the cockpit of Flight 1238 from LA, he was shouting: "The pilots are terrorists. Kill the pilots." He was wrestled to the ground by one of the plane's pilots and several passengers, but not before jets had been scrambled to escort the plane in.
The closure of the Green Line of the Washington Metro was achieved by Kenneth Ranger, apparently no more than a fare-dodger, not with the gun he fired at police officers but the spray can which he used to disperse a cloud of carpet cleanser into the air. Fearful of a biological or chemical warfare attack police closed down the station and the line while technicians carried out tests.
Although the Florida anthrax cases have not yet been proven to be caused deliberately, let alone by terrorists, the timing of the possible attack can scarcely be coincidental, coming as it has in the wake of a massive public debate on the dangers of bioterrorism.
That has impinged hugely on the public consciousness. Supplies of gas masks have all but sold out and doctors report a rush on anti-anthrax antibiotics.
New Yorkers alone filled 14,814 new prescriptions of Cipro in the last week of September and the company that produces it in Germany is stepping up its output.
But doctors warn that taking Cipro and an alternative, doxycyclene, ahead of an attack is likely to be seriously counterproductive by building up a resistance in the body to such medication.
And there is no benefit to civilians from gas masks, experts say,unless they wear them constantly. Why then, the incurably sceptical ask, have members of Congress been given them? Nevertheless the price of masks has soared, with surplus Israeli devices being advertised now on the internet for $100 that were on sale a month ago for $15-20.
There is a demand even for second World War masks and obsolete US M17 masks which must be taken off to change filters.
Full-body, self-contained toxic environment protective suits are available at $10,000 a time, but, the manufacturer warns, "need logistic back-up".
