That sucks. My girlfriend had it a few years back (before I knew her), and she said it was AWFUL, so I feel sorry for Sun. What a great way to start off your time in the good ol' U.S. of A. huh?
I thought you got mono from kissing? Anyways, I wish him well. Seems like a nasty illness he'll have to fight through.
You can get in a multitude of ways, it's just normally associated with kissing (as noted by it's nickname). It's a disease transmitted through saliva, so you can get it by sharing the same glass or beverage as someone that has it.