Hypochondriacs can calm down, this isn't a real disease. The website Itchy Feet published a pretty interesting comic on Sunday August 2nd which parodied the syndromes that vacationers experience when visiting different parts of the world.
There is of course Paris Syndrome, which is a transient psychological disorder. People around the world tend to idealize Paris as the perfect romantic city and when they get there, their expectations aren't met. This can lead to mild depression, aggression, hostility and anxiety.
Jerusalem Syndrome is also very real, you might remember the Simpsons episode where they go to Jerusalem and many characters including Homer become convinced they are the new Messiah. The syndrome is associated with a spontaneous psychosis which certain travelers experience when they arrive in Jerusalem.
London syndrome might not be in any medical journals, but it's very real. People seem to be unable to control themselves in England and tend to jokingly imitate the British accent. Although I have a theory that if England was mostly populated by visible minorities, doing a British accent would be considered racist. But since you tend to think of a white guy when picturing British people, it's perfectly acceptable.
Los Angeles syndrome sounds serious but every city thinks they have the craziest drivers, so this could also be named Montreal Syndrome.
Finally Montreal Syndrome, the only flattering one in the bunch. I'm not sure if it's actually real, but the idea that people who visit Montreal instantly become more polite, helpful and friendly is simply an awesome reputation to have.