Not at all. I work in a school where the Norovirus has been rampant the past month, and both my co-workers have had it.
I just spent 2 days in the emergency room where every 2nd patient seemed to have it.
Maybe my immune system is good because I have been eating well and exercising more, but I have managed to escape it so far...
So going on a cruise in 3 weeks, on a ship that has been hit hard (Ruby Princess) doesn't worry me, because I know they will be taking extra precautions to prevent illness.