Biological weapons weren’t very expensive to begin with, and in recent years their price has plummeted. Today, it’s possible to assemble perfect copies of the world’s most dangerous diseases—pathogens such as the 1918 strain of avian influenza, responsible for roughly one hundred million deaths—in a simple basement laboratory for a few thousand dollars. If anybody can make these weapons, then anybody can use them, and this throws the essential logic of deterrence out the window.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 604