In the book, when Mark's little potato green house explodes into Mars atmosphere he thinks the bacteria (or any life form) is dead since the temperature and air is not life supporting. So, there isn't a possiblity that he transports somekind of virus or bacteria from Mars to Earth. Especially not after he performed one-rocket-manned mission when he left the surface of Mars to meet Hermes crew. But of course, he was so dirty after months of not having a shower they might just be done with it by applying a contamination process for Mark. For his own sake.
Well, The Martian movie and the book can be applied to RL scenarios except one condition. Andy Weir also mentioned this during an interview. Mars' atmospheric density is not dense enough to create a strong sand storm. So that part is just fiction.
BUT there is also a catch. If you are interested, you can take a look at the Mars-One mission page to learn more about a possible Mars mission. They also mention a contamination process for the astronauts. Because you can never know. Some crazy space virus might hold on to you hard enough to arrive Earth.