germ warfare 
noun [mass noun]
The use of disease-spreading microorganisms as a military weapon.While the great powers were spending massive amounts of money on weapons and germ warfare, children were dying of starvation in many lands....
- Kelly was a scientist for the Ministry of Defence, with expertise in weapons and germ warfare.
- While the first recorded catapulting of plague victims' bodies into a besieged city is by the Mongols, Mayor reveals that the ancients also made use of primitive germ warfare.