GERMS ARE EVERYWHERE - you can't get away from them no matter what you do or where you go.
Since it would be rediculous to live in a bubble, Garden!
I agree that the benefit outweighs the risk - exercise, vitamin D (sun), and fresh veggies. Take the normal precautions, and that mask is a good thing too!
I have been working in the yard lately too - it gets me off my rear and lets me use those muscles that have turned flabby!