Infection is POSSIBLE outdoors, but it is much, much less likely. With COVID-19, we're seeing some outdoor spread when people are crowded extremely closely together. So there's some evidence that might suggest that IF there is an outbreak of something, people should mask up at outdoor concerts, pilgrimages, fairs, etc, where there are a lot of people in a tight space. Just walking down the street in most places is not an issue. (Maybe Times Square and I'm sure there are some equal pedestrian bottlenecks in some Asian cities.