The Ames strain is one of 89 known strains of the anthrax bacterium (Bacillus anthracis). It was isolated from a diseased cow that died in Texas in 1981.[1] Researchers at the time mistakenly believed the strain came from Ames, Iowa and mislabeled the specimen. The Ames strain came to wide public attention in association with the 2001 anthrax attacks. Seven letters mailed to media outlets and US Senators on September 18, 2001 and October 9, 2001 contained anthrax bacteria of this particular strain. This strain is a monomorphic disease, mutating slowly if at all.