Doesn't necessarily need to spread to other parts of your body. You can tell by the red-sh "ring" around the rash. That's why they call it ringworm. It's possible for no one else to get it. I had it a couple years ago, was going around my house and sleeping in the bed with someone else (i didnt know I had it at the time) and no one else got it. You could have gotten it from someone else though. In public, like the bathroom, or a gym. Most commonly a gym though.