This article refers to a real life historical event

General Lord Jeffrey Amherst (misnamed in episode "Killer" as "Lord Jeffrey Ashley") was a high-ranking British officer often accused of, in 1763 (specifcally, the last battles of the French and Indian War), giving native Americans the blankets of smallpox victims in order to spread plague among them.  The historical facts of this matter are subtle but on balance implicate not just General Amherst but also other Colonial and later 19th Century U.S. Army officials.  Moreover, such use of biological warfare as a military tactic was actually very common in the 18th Century world, not just against native Americans.