A passenger stands on a balcony of a Royal Caribbean Liner as it docks in Bayonne, N.J., in 2014. File Photo by John Angelillo/UPI | License PhotoSept. 30 (UPI) -- Scores of people on a Royal Caribbean cruise reportedly fell ill with norovirus, prompting CDC efforts to contain the ship's outbreak. The norovirus is a contagious virus more colloquially known as the "stomach flu" that causes vomiting and diarrhea, according to the CDC. CDC officials pointed to predominant symptoms of vomiting and diarrhea of the 71 or so afflicted passengers on board. The Serenade is one in nearly 30 ships in the Royal Caribbean Group family of mega vessels.