A lot of people don't know what the flu really is like - they get a winter cold and call it "the flu", or they get some gastrointestinal bug and call it "the stomach flu". My ex-boss was notorious for the former... he'd have the sniffles but it was "a touch of the flu". Then when a coworker was out for two weeks with the real thing, ex-boss made a lot of derogatory comments because of course HE always came to work, even with "the flu".
The real flu lays most people out flat - congested lungs, bad sore throat, temps well above 100, a feeling like a truck ran over you. The increased mucus production can make you queasy when it ends up in your stomach, but it's not a stomach bug.
BTW I'm not intending to take sides - just making a comment.