i never get sick really.. sometimes if i can feel the flu or something coming on ill stop training for 2-3 days (wouldnt be able to get in good workouts anyway and just going through the motions is a waste anyway), load up on anti oxidants and anti inflammatories (best use natural stuff and no "medicine"), get more sleep and after 2-3 days im ALWAYS 100% again...
working out while youre sick will just drag out the sickness for a week or two imo...
for me its like:
be sick + keep working out = you get your workouts in but for 1-2 weeks youre just at 80-90% at best
be sick + stop working out + do as above = 2-3 days and im back at 100%