Anecdote: I am right now travelling in a metro train bound for Tokyo. Of the 17 people around me, 12 of them have masks on them. Pollen allergy is one that coul

Anecdote: I am right now travelling in a metro train bound for Tokyo. Of the 17 people around me, 12 of them have masks on them. Pollen allergy is one that could explain such high numbers of masked people at this time of the year.