I have been commuting by bike since October 2008 and my fitness and health has dramatically gone up. These past two weeks I decided to drive instead of bike since I have been staying up late doing my research papers for school. I got hit by the flu bug these past 2 days. Fever, fatigue, soreness just straight up hell. Did my immunity took a dive because I wasn't getting the exercise I needed? Who knows?? All I know once I get better I am going on the bike ten fold.
Do any of you had this experience??

When I was commuting (now I work from home), I rarely got sick, while folks at work would be sick all winter it seemed. Probably a combination. You may not be getting as much sleep as you usually do, given your work lately.

Lack of sleep and stress can impact your immunity negatively. Also, The flu is in full swing. Did you get a flu shot??

I have noticed this year, since I started commuting, I have been much healthier... not a single cold, flu or anything. Usually I get at least some sort of illness by this time in the year but i feel great, even when the kids have been sick I haven't caught it...

You don't want to know what your car seat or air filter look like under a microscope... fresh air is good for you!

Exactely, I was going tosay that. Do not forget the AC! Terrible stuff.

Since I started riding I get sick less often, and when I do it's not as severe and recovery is faster. I also seem to miss fewer days than my coworkers. I figure if I'm too sick to ride, I'm too sick to work; if I'm too sick to work, I'm too sick to ride.

I'm not sure, but I've had a nagging sore throat for the past couple weeks, and cycling definitely makes it worse. For once, it's good that the weather is bad this week so i won't ride as much...