CDC : `` I teach them to sing 'happy birthday ' to yourself twice to make sure they wash for at least 20 seconds , '' Harrison said . Elementary kids get eight to 12 colds or cases of the flu every school year . Comment: Hand-washing , sleep , regular exercise and a healthy diet are key to preventing illness .
CDC : Elementary kids get eight to 12 colds or cases of the flu every school year . Comment: Hand-washing , sleep , regular exercise and a healthy diet are key to preventing illness .