Norfolk is in Virginia. A navy center. Norwalk is on the ships, actually Norwalk is everywhere but you only hear about it on the ships where there is a confined enviroment and it makes the news.
Wash your hands frequently, avoid touching your eyes and nose, and avoid sneezing people. Also, take some hand sanitizer wipes with you so if you're in an area where you are touching a lot of common, public, items, such as casino chips, you can clean your hands more frequently.
It's Norwalk and it was named after a school where it was very prevelant. Basically it is the stomach virus and the only thing more common that it is the common cold. You have had it many times in the past and will have it again. Problem is when it happens on a cruise ship people go nuts. The best way to prevent it is using good hygene namely wash your hands often and always after using the restroom.