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Merson MH, Hughes JM, Wood BT, Yashuk JC, Wells JG. "Gastrointestinal illness on passenger cruise ships," JAMA, 1975, 231:7 (Feb 17), 723-7

Medical logs of 2,445 cruises taken by 38 vessels over a 20-month period beginning Jan 1, 1972, were reviewed. On 92% of the cruises, the recorded incidence of gastrointestinal illness was 1% or less; on 2% of cruises, it was 5% or greater. The actual incidence of gastrointestinal illness determined by a questionnaire survey of passengers sailing on nine cruises was found to be at least four times as high as that recorded in the medical logs. Although the cause of the illnesses was not known, there was evidence that transmission took place aboard ship. A survey of food-handling practices and water systems aboard selected ships demonstrated a significant potential for transmission of foodborne and waterborne disease.

Merson MH, Tenney JH, Meyers JD, Wood BT, Wells JG, Rymzo W, Cline B, DeWitt WE, Skaliy P, Mallison F. "Shigellosis at sea: an outbreak aboard a passenger cruise ship," American Journal of Epidemiology, 1975, 101:2 (Feb), 165-75

  Between June 23 and June 30, 1973, 90% of 650 passengers and at least 35% of 299 crew members experienced a diarrheal illness during a 7-day Caribbean cruise aboard a passenger cruise liner. Symptoms were consistent with shigellosis, and Shigella flexneri 6, Boyd 88 biotype, was isolated from rectal swabs taken from 8 to 35 ill passengers and 33 of 294 crew members. Epidemiologic evidence incriminated the ship's water, including ice, as the probable vehicle of transmission, and elevated coliform counts were found in potable water samples obtained aboard the vessel at the peak of the outbreak. Potential sources of contamination of the vessel's potable water supply were investigated, and improvements in the loading and chlorination of potable water were recommended.