They clean it, it doesn't have any germs or any trace of anything that happened to it previously. Water is cleaned, so you may have just been drinking water that someone showered in, but it has been cleaned. Same goes for forks and spoons at a restaurant. People's mouths have been all over them, but they have been cleaned, so don't worry.
I am currently reading Prodigy written by Marie Lu. I absolutely LOVED Legend which is the first book in this trilogy. Since I loved the first one so much I wanted to immediately continue on with the rest of the series. Marie Lu is an amazing author and has not ever disappointed me. I tend to not like books with lots of love. Marie Lu's Legend trilogy does indeed have that, but it is not overpowering. With all of the suspense, mystery, and action this book has, it couldn't be better. Such a brilliant idea with parts in the book that touch the heart. Great job Marie Lu.