Norovirus illness is not related to the flu (influenza), which is a respiratory illness caused by influenza virus. Norovirus is a very contagious virus. You can get norovirus from an infected person, contaminated food or water, or by touching contaminated surfaces.orovirus illness is not related to the flu (influenza), which is a respiratory illness caused by influenza virus. Norovirus is a very contagious virus. You can get norovirus from an infected person, contaminated food or water, or by touching contaminated surfaces.