What gamble did washington take to face the smallpox epidemic at valley forge

Whether or not it was brought by the troopships, America was in the middle of a smallpox epidemic. 

The majority of Americans had lived three generations without contact with smallpox and were more likely to die from it, about two out five Americans survived infection. It was the reason for the high casualty rates among surrendered colonists held in British prison ships, only one in ten survived imprisonment. 

Washington dealt with the disease in Valley Forge by inoculating healthy soldiers with pus from infected troops which was introduced into the bloodstream directly by a small cut made for the purpose. Pus is mainly a build up of dead bacteria, so soldiers treated in this way had a chance of building up resistance to the live disease. Some of them did die from this procedure, but his main army pulled through.