Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Norovirus Infections ?
    ### Response:
    Noroviruses are a group of related viruses. Infection with these viruses causes an illness called gastroenteritis, an inflammation of the stomach and intestines. It can spread from person to person, or through contaminated food or water. You can also get it if you touch a contaminated surface.
    