Here's why you need to wash your hands for 20 seconds, according to physics

Sep 6, 2020
"The model showed that particles are attracted to the rough surfaces, and a certain amount of energy is required to enable the particles to escape into the fluid. A faster motion of the hands creates a stronger flow of fluid and removes the particles more easily"

I wonder if that, in-part, is why the elderly and disabled appear to catch illnesses more than you would hope...

A combination of a weaker immune system with more exposure to risk.