I was sick last week and didn't exercise much at all. I had flu-like symptoms, a very bad cough, and side pain, so I figured it was best to take it easy. I went stir-crazy, but I told myself I could get right back on my normal plan once I was healthy again.
Jay is VERY right about the sick body needing nutrients. My initial plan was not to go over my sedentary maintenance (and on most days, I didn't), but one day, I got very hungry and devoured the universe. I made sure these foods I ate were all healthy, fresh foods with good amounts of protein and whole grains. I felt bad about eating so much, BUT the next day, I felt 348290739 times better! I think my body needed it.
Luckily, sickness usually doesn't last too long, in the grand scheme of things. Take Vitamin C and Cold Eeze, drink some green tea with honey, and feel better.