Small Pox was less a weapon and more a fact of life during the American Revolution. Washington had to cope with the problem in keeping his troops fit to fight. Several Generals died of the disease and many privates. At first the American approach to the disease was to isolate those with the disease from others. When newly recruited troops arrived in camp, they would be isolated for several weeks before being sent to their units. As the war progressed, Washington allowed innoculation to occur: a weak form of the disease was introduced and built immunity. Those innoculated were segregated from the others until the active symptoms were over.
There are stories that circulate, and I don't know if they can be proven, of smallpox infected blankets being given to the indians to introduce the disease and weaken them as enemies. Perhaps others more knowledgeable can add references to allow that to be substantiated.
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