It's horrendous! Hit me at 3 am Tuesday and didn't let up until about 4 am today. And, I still don't feel back to par, just upright. Haven't eaten since Monday. In fact, Tuesday morning alone, I lost 5 pounds, and a total of 8 after this thing. The last time I experienced anything like that was food poisoning a couple years ago. I did consider perhaps this was FP rather than flu, but I have no clue what I could have eaten that would bring it on. Stomach cramps like labor pains, body aches like never before, freezing cold laying in bed under a pile of blankets, nearly passing out in the bathroom, drenched in sweat.........it was horrible! So, learn from me. Bump up the Vitamin C, stay out of crowds, and wash those hands!!