For me,
Chills so bad it was into the shower to warm up, then sweats that would soak the bed. Shakes bad, jumped at every noise, insomnia from hell, I had aural hallucinations, heard a clock chime when it was not and music. Oh yes and then there is the severe nausa and vomiting with nasty diarrhea all at the same time. Inability to think at all.
And that's just the first 6 hours or so...
No fun.
If you have rough symptoms, a Doctor is well advised.