Attenuated? Ooo, that sounds dangerous....

Spraying scenes from the Aum Shinrikyo headquarters building (photographs taken July 1, 1993, by the Department of Environment, Koto-ward).

Terrorists and microbiology don't seem to mix well. Terrorists seem better suited to explosives and have managed to successfully carry out numerous devastating bombings. But the meticulous and laborious work involved in microbiology seems challenging for the average terrorist who would probably rather be blowing something, someone, or themselves, up.

From the pages of 'epic fail' I bring you the surprisingly little known story of Aum Shinrikyo and anthrax. I am not making this up, everything that follows is fairly well documented (eg. this CDC report), it just isn't very well reported.

Aum Shinrikyo, who have apparently changed their name to Aleph, are a Japanese religious movement, or cult depending on where you draw the line. They are most notorious for their Sarin attack on the Japanese subway in 1995 that killed 12 commuters, seriously injured 54 and affected about a thousand more.

Two years before this, in July 1993, Aum Shinrikyo members dispersed a liquid suspension of Bacillus anthracis (anthrax) from the roof of an eight-story building in Tokyo. Although residents complained of foul odors the spraying went on for at least four days until demands from local residents forced Aum Shinrikyo to stop. There were no known human cases and, at the time, no-one realized an attack had even taken place. The incident was largely forgotten until the 1995 subway sarin gas attacks. Confessions of Aum Shinrikyo members revealed the plot and samples collected in 1993 were eventually analyzed in 1999 and found to be anthrax. The obvious question is why the anthrax attack plot had failed. The consensus seems to be that the would be bioterrorists did just about everything wrong.

• Spraying during the day was a bad move, sunlight inactivates the spores and heat radiating from concrete and asphalt makes the spores rise rather than fall.
• The spore concentration that was sprayed was about 10⁴/mL - many orders of magnitude less than the 10⁹ to 10¹⁰ organisms/mL considered to be optimal.
• The spraying device was very inefficient and apparently the nozzles clogged repeatedly and the device itself broke down several times.
  
• But I saved the best for last. The strain of anthrax used was an attenuated (weakened) strain used to vaccinate animals in Japan. This strain is generally regarded as nonpathogenic for immunocompetent people.

Bioterrorism - it's not as easy as they make it look in the movies.