Handwashing: it's something you do multiple times a day, every day. It's probably so ingrained into your daily routine that you rarely give it much thought. However, when done properly, it's the single most effective way to prevent the spread of germs. December 4-10 is National Handwashing Awareness Week, and also the time of year when influenza (flu) viruses in the United States start to peak. If you follow the 4 Principles of Hand Awareness, as advised by the Centers for Disease Control and Prevention, you can virtually isolate yourself from the germs people around you may be spreading: