Patron strain of the Mexican flu

A hangover.

(After a late night out drinking with colleagues)

Coworker 1: Has anyone seen Sarah this morning? It's already 10:00 and this project is on a deadline.

Coworker 2: Last I saw her was at 2:30 AM when we were leaving the bar after a really late happy hour. I think she called in this morning with the flu.

Coworker 1: Yeah. Must be the Patron strain of the Mexican flu that's been going around.