Norovirus is a communicable disease. If you are in direct contact with someone who is infected with the virus, you are more likely to catch the virus.
Apart from this, eating food or having liquids that are contaminated with the virus, touching surfaces or objects contaminated with norovirus and then touching the face or eating something out of the same hands without washing can also help the virus reach your body.
The food which is grown or harvested with contaminated water can also spread the virus.