There is actually plenty of data to suggest that re-usable, cloth masks are actually harmful because they collect bacteria and moisture (which feeds MORE bacteria), and concentrate it directly in the respiratory path of the wearer. A physician friend called cloth masks "sewers" that will only lead to respiratory illnesses besides Covid. Couple that with the fact that many wear their masks with their nose not covered only leads to a false sense of security in the wearer and actually encourages them to violate social distancing (another dubious "scientific" concept).