What is the definition of Watershed Infection?

A "watershed infection" is like when your favorite band decides to play at your birthday party, but the catch? They're wearing a t-shirt that says "Bleach!" and their last song was a cover of "I Want to Hold Your Hand" with a side note of "I'm just a washed-up star." This is basically your personal public health crisis, courtesy of a musical misunderstanding.

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Here's an edgy example sentence: "The watershed infection at the comedy club was so bad, the audience decided to stage a protest in favor of watermelon pizza over existential dread."