Sneezes and Washing Hands

Last Friday for health we learned that sneezes can travel at 160km/hr and are caused by irritation in the nose. 
In Room 6 we use tissues and handkerchiefs when we sneeze.
Mr Mac talked about washing hands. He said you must wash your hands for as long as it takes to sing a special song.
It was Charlotte's birthday yesterday. How is this and Mr Mac's advice connected?