Bacteria are the most common living things on earth. You carry them wherever you go. They live on your hands and under your feet. They hide in your mouth, nose, and eyes. Most of them couldn't hurt a flea. But if conditions are just right, they can cause big problems. Want to know more? This Stuff Can Be Infectious. Read About: how germs can invade your body; how a visit to the hospital turned deadly; the tools and equipment health-care workers use...