Norovirus is a highly contagious virus for a variety of reasons. First, anyone is susceptible to get the virus, regardless of your age, sex, or health condition. Even the healthiest of individuals with strong immune systems can get infected with norovirus. Additionally, you can get norovirus more than one time, as there are many different strands. So you may get one type of norovirus at one time and a completely different type another time.
Spreading the virus before you know you have it
Another reason norovirus is so contagious is because you may begin spreading the virus to others before you even know you have it. For example, if you acquire the virus, it will be alive and well in your digestive system before you start feeling any symptoms at all. Plus, it can stay in your system for more than two weeks after your symptoms have passed. 
This means that you can be contaminating surfaces and spreading the virus before you realize you have it and after you’re over the symptoms. You can spread the virus by shared utensils, coughing, shaking hands with others, handling food for others, kissing, and more. However, you are most contagious during the time your symptoms are prevalent and a couple of days after they’ve subsided.
Norovirus is a hearty virus
Due to its hearty nature, norovirus is the leading cause of viral outbreaks in America. The main culprit of such outbreaks are infected restaurant or food workers that touch foods before serving. You may hear of various places like nursing homes, schools, daycare centers, and cruise ships having a norovirus outbreak, as the virus can spread very quickly throughout the enclosed population.