Would Bubonic Plague make a good weapon?
A 1970 World Health Organization assessment asserted that in a worst-case scenario a dissemination of 50 kg of Yersinia pestis in an aerosol cloud over a city of 5 million might result in 150,000 cases of pneumonic plague. Of those, 80,000 to 100,000 cases would require hospitalization, and 36,000 victims would be expected to die.
Of course there are numerous difficulties involved in getting 50kg of bacteria into an aerosol cloud. You could just breed infected fleas instead but, as the video says, they may well come back to bite you...