Protection for the Petri dish. Not the wearer. I personally have no concern with protecting the Petri dish as I am more than capable of staying home when I have the flu/cold and sneezing/coughing so that it does not spread if the need arises.
Well fine stay home. I always avoid crowds during flu and cold season. But sometimes I have to go out. If you have no objections I’ll wear a mask. I mean if it’s OK with you of course. 😏