It takes time, at least 20 seconds, according to the experts at the Centers for Disease Control and Prevention. And there's a technique to it.
"If you pay attention to the way you wash your hands, usually you rub your palms together and the part of the hand that does the most touching of other things is the fingertips. So we often tend to miss the fingertips."
Elaine Larson is an associate dean at Columbia University's School of Nursing. She says alcohol gels are a good alternative when you can't get to a sink.
"And the time when the viruses are the most catching, if you will, is right after somebody coughs or sneezes on their hands and then they touch the surface and then you touch it. So if you are out in public where you need it most, you can't run to a sink. So you carry alcohol sanitizer. It works faster than hand-washing and it kills just as well."
For more information
Mayo Clinic: ''Hand-washing: Dos and Donts