We have over 26 miles of paved path here that you can walk/run/bike on, but how do you know the person you just passed did not just spread the virus on the path breathing heavy before they passed you???
That's possible for sure. My work daily health questionnaire asks for contact of 10 minutes or more with a suspected case or someone else who is exhibiting signs. Indoors is worse, indoors with poor ventilation worse still. Hey, I've got a great idea, lets go sit in a bar and tip a few. Or, like they did in a nearby town, sing together in a choir, they almost all got it.