I don't understand how Quarantine is a powerlevel source. I always get shit exp whenever I play it. I've seen youtube videos where the infected just kill the humans really quickly in a group, but what is that suppose to accomplish? I don't really understand. So I have some questions if you can please answer them.

Q) How does powerleveling in it work?
Q) How is the exp distributed?
Q) Why is Quarantine a powerlevel source?
Q) What makes it better then Fireteam?
Q) Which servers does it normally take place in?
Q) Are there any equipment required?