Grey's Anatomy, Season 10

Meredith:
[voice over] The average person touches their face about eighteen times every waking hour. That leaves you susceptible to infection about one hundred times a day. Infection has a nasty habit of taking advantage of our everyday behaviours. It spreads by touching doors, desks, elevator buttons, pens, sharing cups, even money. All we can do is try our best to prevent it from spreading because once it's out there, the infection usually wins.