We probably all had an illness while training for a race. But the closer race day, the more frustrating it can be when we are not able to run. I just had a nasty chest infection last week, about a month before Prague Marathon. Had the same issue a few years back while training for my second marathon but this time around I was smarter. Learned from past mistakes I made and I think I made the right decision this time around. I need to mention, that I don't have a medical background and that I speak from my experience on the topic. But still I think, that the advice you'll get will help you through injury or illness while training for a marathon.