germ warfare

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The use of injurious microorganisms, such as bacteria or viruses, as weapons in warfare.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The use of harmful microorganisms as a weapon of war.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the use of harmful bacteria as a weapon