In February of 2001, people in Victoria, Toronto and Ottawa, the latter a Member of Parliament, received letters purported to contain the causative agent of anthrax. Anthrax has been with us since antiquity. Accounts by the Huns during their sweep across Eurasia in 80 AD describe mass deaths among their horses and cattle attributed to anthrax. Indeed, loss to European livestock in the 18th and 19th centuries stimulated the search for a cure. Or, and this is the insidious aspect with respect to bio-terrorism, B.anthracis can hunker down and wait out the nutritionally bad times by becoming dormant.
Tough times trigger the formation of a spore.
The spore is designed to hibernate until conditions are conducive for growth and reproduction. Then, the spore resuscitates and active life goes on again. Tests have shown that the spore can survive up to 60 years in the soil. The spore form can be easily inhaled. Only 8,000 spores, hardly enough to cover a snowflake, are sufficient to cause the pulmonary disease when they resuscitate in the warm and humid conditions of the lung.