In 1781 the Revolutionary war had started
The <span>name given to the British practice of taking americans sailors from their ships and forcing them to serve in the British army was "impressment," since the British were "pressing" the Americans into service. </span>
The most deadly illness the pioneers have faced was Oregon Trail, it was spread by for hunting food, picking berries, and most of all this terrible game kids used to play that made them realize the Oregon Trail was real. It also lead up to bad fever, cholera, and dysentery.
This is the main reason of the deadly illness pioneers had.
Hope this helps you :)