Hundreds of Tough Mudder racers infected by rugged, nasty bacterium

Aeromonas hydrophila (A. hydrophila) : https://en.wikipedia.org/wiki/Aeromonas_hydrophila

A bacteria version of The Last of Us (or, less fancifully, COVID-19) happening because of Tough Mudder or Burning Man or another mass event of people crawling through wet mud, would really be quite something.