"Today" host Matt Lauer and Dr. Philip Tierno, author of "The Secret Life of Germs: What They Are, Why We Need Them, and How We Can Protect Ourselves Against Them," trekked around Manhattan and analyzed what they found in everyday spots like the subway and the gym while discussing that germs are everywhere and impossible not to pick up.

80 percent of all infectious diseases are passed by human contact, either direct or indirect? That includes viruses like pneumonia, salmonella, and the common cold. But with proper hand washing, you could avoid carrying around many potentially infectious diseases.

Dr. Philip Tierno is director of clinical microbiology at the New York University Hospital Center and the author of "The Secret Life of Germs,” says, “It takes 20 seconds to appropriately wash your hands, getting in between your fingers, getting on top of your knuckles, getting under your nail bed with at least one swoop each time with a lot of soap on and then rinsing. The Centers for Disease Control recommend singing "Happy Birthday" twice through for an effective wash.”