Speaking as a retired hospital RN who knows a thing or two about infection control and isolation procedures and has read anything published by infectious disease specialists on coronavirus transmission, chances of being infected while walking, hiking, and biking are close to zero. An infected person exhales virus by coughing or sneezing and in lesser amounts by talking and breathing. The virus is quickly dispersed in the atmosphere outdoors and the more windy it is, the faster it dissipates. Think of what happens to exhaled smoke outdoors for comparison. A study of 7,000 COVID patients that traced how they became infected found that two people were infected during conversation outdoors. That’s two out of 7,000. Someone would basically have to cough, sneeze, or pant in close proximity to your face to infect you during outdoor activity. I’ve been hiking a lot lately. I worry about being infected by careless people in Target and Vons, not by other hikers and runners.