Bioweapons development and attempted use by terrorist groups has emerged as a prominent issue within the past two decades. An early terrorist attack in the United States occurred in 1984 with the spread of salmonella in salad bars in Oregon by members of the Rajneeshee cult as a means to sicken local citizens to prevent their voting in an upcoming election. What turned out to be a "trial" attack proved successful, causing about 750 cases of salmonella poisoning 45 of which required hospitalization.
Between 1993 and 1995, a religious sect in Japan, the Aum Shinrikyo, sprayed botulinum toxin and anthrax in downtown Tokyo as many as ten times without success (why the attacks failed remains unclear, but it is suspected that a non-infectious "vaccine" strain of Bacillus anthracis was used, and what agents were released were not properly "weaponized"). Unfortunately, the sects 1995 sarin attack in Tokyos subway proved more effective, killing 12 commuters and sickening thousands.