I just had the flu hard-core for about 3 days, after that it tapered off a bit but i was VERY lethargic and had a horrible nighttime cough that disrupted the all-important recovery sleep, so i tried to nap as much as possible during the day.
It's now 2 weeks from the onset of my symptoms and i'm still battling sinus drainage and that weak feeling. My only workout during this time has been 30 minutes of low-intensity cardio which just left me feeling weaker than when i started, so I succumbed to the sickness and haven't worked out during this time and it's been driving me nuts.
Tonight i'm hitting some low-intensity cardio and delts, but not pushing hard because I do not want to relapse!
Best advice is to stay out of the gym, sleep as much as you can, take lots of echinacea & zinc and drink a lot of water and some OJ!
Oh and massages! they help to work the toxins out of the sytem. I had 2 within 3 days last week and I really think it helped to get the bug out!
I hope you get to feeling better soon!