Sweat carries germs and when you are sharing lots of equipment in a sweaty gym it is very easy for you to pick up the germs of others. What are some of the precautions you take while at the gym to avoid diseases?
I don't go to the gym very often, but when I get there, I usually shower afterward with a good antibacterial soap, and I always wash my hands afterward. I also never share water bottles (or any other drinks) with other people. Other than that, I'm not too paranoid.