For a useful summary of what we know or suspect about becoming infected by the coronavirus there’s a good summary on Bloomberg today - https://www.bloomberg.com/news/artic...-you-quicktake

As I said recently, it’s a disease mostly spread by extended contact in confined spaces. Interestingly the Apps that purport to track potential contacts all focus on one time period - 15+ minutes. Spending 30 seconds in an elevator or passing someone in a shopping centre just doesn’t cut it. The arguments for masks are strongest in indoor or static environments (such as a football stadium where attendees don’t move around) and much less for outdoor protest marches such as the ludicrous People Of Colour Lives Matter