The symptoms you feel are caused by your body fighting the viruses. Fever is your body heating up to try to overheat and kill the virus. Vomit/Diarrhea is your body getting rid of whatever you ate via the nearest exit, mouth/butt. Snot, sneezing, etc is your sinus creating a mucus layer of protection to try and catch and remove the illness. Coughing is when that mucus makes it into your lungs.

Slip steam only works well at extremely fast speeds. The distance required to slip stream is too small to be safe for highway driving. You might get some effect behind a transport truck, but not much.

How it works. As the 1st vehicle moves, it is pushing air away from the vehicle. This creates a small pocket of slightly less dense air behind the vehicle. If a 2nd vehicle can follow behind, in that pocket of less dense air, then it has less wind resistance slowing it down, giving it the slip stream advantage.