Besides the obvious answer of going home, homesickness may be unavoidable. To make it better, take lots of pictures on your trip and lots of reminders of good times. Also find a way to communicate with your loved ones back home. Set a time once or twice a week that you talk to them online or on the phone. For really long distances, I use Skype. I can call any phone from my computer for dirt cheap.
it is not a disease as such but the best thing to do is to keep your mind off it and occupy yourself in something else (dont stop to think obout home sickness )