Robert Stevens (photo Editor) - Anthrax Material

Anthrax Material

The letters sent to the media contained a coarse brown material, while the letters sent to the two U.S. Senators contained a fine powder. The brown granular anthrax mostly caused skin infections, cutaneous anthrax (9 out of 12 cases), although Kathy Nguyen's case of inhalation anthrax occurred at the same time and in the same general area as two cutaneous cases and several other exposures. The AMI letter which caused inhalation cases in Florida appears to have been mailed at the same time as the other media letters. The fine powder anthrax sent to the senators mostly caused the more dangerous form of infection known as inhalational anthrax (8 out of 10 cases). Postal worker Patrick O'Donnell and accountant Linda Burch contracted cutaneous anthrax from the Senate letters.

All of the material was derived from the same bacterial strain known as the Ames strain. Prior to the attacks, the Ames strain was believed to be a common strain isolated from a cow in Iowa. After the attacks, the investigation discovered that it was a relatively rare strain isolated from a cow in Texas in 1981 - a critical fact in the investigation. First researched at the United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Maryland, the Ames strain was then distributed to sixteen bio-research labs within the U.S. and three other locations (Canada, Sweden and the United Kingdom).

DNA sequencing of the anthrax taken from Robert Stevens (the first victim) was conducted at The Institute for Genomic Research (TIGR) beginning in December 2001. Sequencing was finished within a month and the analysis was published in the journal Science in early 2002.

Radiocarbon dating conducted by the Lawrence Livermore National Laboratory in June 2002 established that the anthrax was cultured no more than two years before the mailings. In October 2006 it was reported that the water used to process the anthrax spores came from a source in the northeastern United States.