Cause
Botulism is caused by toxin (poison) produced by Clostridium botulinum bacteria. This toxin affects your nerves and, if untreated, can cause paralysis and respiratory failure. C. botulinum toxin is one of the most powerful naturally occuring toxins. Exposure to the toxin, particularly in an aerosolized (spray) form, can be fatal.
C. botulinum has been made into bioweapons by rogue states and is one focus of current efforts to counter bioterrorism.