Ugh . Three outbreaks of illness affecting more than 100 people each have been reported aboard two cruise liners -- two of them in back-to-back cruises of the same ship -- according to the nation 's leading health protection agency . The double dose of ill-fated cruises struck the Royal Caribbean 's Grandeur of the Seas , the Centers for Disease Control and Prevention said Friday . During the ship 's April 5 to April 12 cruise , 105 of the nearly 3,000 passengers and crew were affected -- primarily with vomiting and diarrhea , the disease agency said . During the ship 's cruise the prior week , 117 passengers and crew members were struck , according to the CDC . Two CDC Vessel Sanitation Program environmental health officers and an epidemiologist were to board the vessel in Baltimore , Maryland , on Saturday to conduct an investigation . Specimens were being collected to be sent to the CDC lab for testing . `` We 'll be working with both the medical teams as well as the crew on board the vessel and the cruise line with doing follow ups , '' Bernadette Burden , a CDC spokeswoman , told CNN affiliate WJZ . `` Really taking a look at their cleaning , sanitation and hygiene practices that are being employed on the ship to interrupt the spread of disease . '' But the ship 's owners were planning to plunge onward , departing as scheduled at 4 p.m. Saturday on the next cruise -- seven nights to the Bahamas . Royal Caribbean told WJZ that any would-be passengers feeling a little queasy about the prospect of leaving Saturday aboard the twice-stricken ship could reschedule . The third outbreak affected Princess Cruise 's Crown Princess during a week-long cruise ending Saturday . In all , 152 of the more-than 4,000 passengers and crew were sickened . A lone CDC Vessel Sanitation Program environmental health officer was to board the ship upon its arrival Saturday in Los Angeles `` to conduct a targeted environmental health assessment , and evaluate the outbreak and response activities , '' the CDC said . The chief suspect behind all three waves of illness is norovirus , a highly infectious virus that can be picked up through contaminated food or water or by touching contaminated surfaces . It causes inflammation of the stomach , intestines or both , often leading to stomach pain , nausea , vomiting and diarrhea . Each year in the United States , it causes 19 million to 21 million illnesses , and contributes to 56,000 to 71,000 hospitalizations and as many as 800 deaths , CDC says . Cruise ships are a prime target . `` We have so many people together in a closed environment , eating in the same place , '' Catherine Troisi , associate professor of management , policy and community health at the University of Texas School of Public Health , told WJZ . `` That 's why you see it . '' How the Navy avoids norovirus . Are cruise ships floating petri dishes ? Is your cruise safe ?
The Royal Caribbean 's Grandeur of the Seas was struck during back-to-back cruises ending Saturday . That wo n't stop it from setting off Saturday for a third cruise . Norovirus is a common cause of diarrhea and vomiting among cruise ship passengers . It causes as many as 800 U.S. deaths per year , CDC says .