An interesting piece:
https://www.scientificamerican.com/article/dirty-money/
“Studies have piled up in recent years describing exactly how filthy—specifically how bacteria-laden—our dollars and cents can be. Fecal bacteria and other pathogens may have hitched a ride from someone’s hands, nose or apron onto our cash. And yeast or mold might have taken hold, too. The result could be a durable risk to our health whenever our money changes hands.”
“Studies have piled up in recent years describing exactly how filthy—specifically how bacteria-laden—our dollars and cents can be. Fecal bacteria and other pathogens may have hitched a ride from someone’s hands, nose or apron onto our cash. And yeast or mold might have taken hold, too. The result could be a durable risk to our health whenever our money changes hands.”