June 13, 1986

Three outbreaks of gastroenteritis occurred on two Caribbean cruise ships between April 26, and May 10, 1986. More than 1,200 persons developed gastrointestinal illness; no deaths were reported. At least one of the outbreaks appears to be associated with Norwalk virus.

Two outbreaks occurred on two consecutive 1-week cruises of the Holiday, a Carnival Cruise Line ship. Between April 26 and May 3, a total of 392 (25%) of 1,550 passengers and 30 (4%) of 679 crew who completed questionnaires developed gastroenteritis. Eighty-six percent had diarrhea; 62%, vomiting; 36%, headache; and 26%, subjective symptoms of fever. The outbreak peaked on the fifth and sixth days of the cruise.

On the next voyage, from May 3 to May 10, a second outbreak occurred on the Holiday in which 321 (22%) of 1,470 passengers and 48 (7%) of 658 crew developed gastroenteritis. A sanitation inspection initiated by CDC on May 3 revealed deficiencies related to water chlorination record-keeping, food preparation and holding, and potential contamination of food.

A detailed account of these deficiencies was provided to the ship’s management at the end of the investigation on May 3, and recommendations were made to prohibit food-service personnel from working while ill and to correct the sanitation deficiencies. A week later, when the inspection was completed, several deficiencies similar to those of the previous week were noted. The final vessel sanitation inspection score on May 10 was 18 out of a possible 100 points (passing = 85).

An outbreak of gastroenteritis also occurred on Holland America Cruises’ Rotterdam. Between May 3 and May 10, 405 (37%) of 1,108 passengers and 35 (6%) of 554 crew who completed questionnaires had a gastrointestinal illness. Eighty percent of ill passengers had diarrhea; 78%, vomiting; 41%, headache; and 32%, subjective symptoms of fever. Mean duration of illness was 2.4 days, and 76% of ill passengers were confined to their cabins during the illness. A sanitation inspection by CDC on May 9 and May 10 revealed numerous deficiencies related to food and water sanitation; the sanitation inspection score was 16 out of a possible 100 points.

A detailed account of the deficiencies was presented to the ship’s management on May 10 following the inspection, and recommendations were made to prohibit food service personnel from working while ill and to correct the sanitation deficiencies.

Bacterial cultures of stool specimens from the first Holiday outbreak did not yield any recognized pathogens. However, an eightfold or greater rise in antibodies to Norwalk virus was demonstrated by biotin-avidin immunoassay (1) in paired sera obtained from three ill Holiday crew members who had suffered gastroenteritis during the April 26-May 3 voyage; Norwalk antigen was detected by biotin-avidin immunoassay in two of six ill passengers from the same voyage. Laboratory studies of specimens and epidemiologic analysis of questionnaires from ill passengers and crew from all three outbreaks are continuing. Reported by Div of Quarantine, Center for Prevention Svcs, Enteric Diseases Br, Div of Bacterial Diseases, Respiratory and Enterovirus Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note
Editorial Note: Outbreaks of gastrointestinal illness on cruise vessels have been caused in the past by contaminated water and by food consumed on the ships or on shore visits (2). Person-to-person transmission has also been strongly suspected on some occasions–in one case, in the setting of repeated outbreaks on consecutive cruises (3).

Laboratory findings implicated Norwalk virus as the pathogenic agent on the first of the Holiday outbreaks. However, all three outbreaks had epidemiologic features characteristic of epidemics of Norwalk virus gastroenteritis. These include: (1) a high attack rate in adults; (2) a high frequency of vomiting; (3) short duration of illness; and (4) absence of identified bacterial pathogens (4).
It is not yet clear whether food or water were vehicles of infection in these outbreaks or whether sanitary deficiencies contributed to the risk of outbreaks of viral enteric disease on these cruise ships.