Bacteria bags disease for everyone unless washed between shopping rounds.
String bags would get my vote...I take them along when traveling coz’ they take up hardly any room in your purse and can be whipped out if your purchase stuff. They just keep expanding, expanding and expanding as you stuff things in...and they are washable. Lots of European stores don’t provide free bags...my Mum used sturdy canvas bags, and leather bags, for toting home groceries when we lived there...and I can’t recall they were ever washed, although she sponged off obvious stains. The break down in the food chain wasn’t as prevalent then, and food wasn’t imported much as now. Maybe a partial answer to disease prevention is buy locally.