Inspections sharply reduce diarrhea outbreaks on cruise ships

December 12, 2002

A new report links diarrhea outbreaks aboard vacation cruise ships to the scores they get on mandatory sanitation inspections. It found that as cruise lines improved their sanitation practices in the 1990s, outbreaks declined.

The study also links the inspection pass-fail mark of 86 percent for ships to the incidence of what is popularly but inaccurately known as "stomach flu" -- gastrointestinal symptoms often stemming from water and food contamination among groups of people in close contact.

The research findings are scheduled to appear in the April 2003 issue of the American Journal of Preventive Medicine but will be available on that journal's Web site ( ) this month. The data is being released this week in conjunction with a Centers for Disease Control and Prevention report analyzing a recent wave of diarrhea and vomiting among cruise passengers.

Recent problems experienced by passengers on Holland America Line's Amsterdam and Disney Line's Magic were probably caused by a Norwalk-like virus, according to the CDC. Other diarrhea and vomiting outbreaks have affected Carnival Cruise Lines' Fascination and P&O Cruises of London's Oceana. Several hundred passengers fell ill on these ships in late November and early December.

The journal study doesn't single out any particular cruise line for sanitation violations or increased frequency of diarrhea outbreaks, and the lines affected did have high scores on their most recent inspections.

As cruise ships improved their scores in the 1990s, the number of diarrheal illnesses on those ships fell, according to Elaine H. Cramer, M.D., M.P.H., of the CDC's Vessel Sanitation Program of the National Center for Environmental Health.

From 1990 to 2000, inspection scores gradually increased from an average of 89 to an average of 93 out of a best possible score of 100. During this same period, the rate of normal diarrheal illness dropped 44 percent, while the rate of outbreak cases (where more than 3 percent of passengers fell ill) dropped 27 percent.

Since 1998, inspection scores have been posted on the CDC's Vessel Sanitation Program Web site (, allowing better public access to information and giving cruise lines an extra incentive to perform well.

Inspection scores and information on the incidence of diarrheal disease aboard cruise ships comes from a database maintained by the Vessel Sanitation Program. All cruise ships arriving from international ports into U.S. or Canadian ports with 13 or more passengers are subject to inspection.

The program grades each ship on its overall sanitation after examining its water supply, food preparation and employee hygiene. It also looks at the ship's equipment maintenance, waste disposal, toilet and hand-washing facilities and pest and toxic substance control. Ships that do not score at least an 86 on the inspection fail and must remedy any sanitation problems and be re-inspected within four weeks of the failing grade.

Smaller-sized ships, older ships and ships that were part of small fleets were more likely to receive failing sanitation grades than their larger and younger counterparts, according to the study results.

All ships log the number of passengers visiting the infirmary for diarrhea treatment. Since many passengers probably treat themselves with over-the-counter medications or avoid going to the infirmary for other reasons, it's likely that the number of diarrhea cases on each cruise is actually higher than reported, say the researchers.

"The findings from this study suggest an effective public health-industry approach to prevention through a program that benefits the traveling public and maintains public health standards," says Cramer. The report specifically recommends posting on the CDC site the inspection records of each ship over the preceding 12 months and striving for an international inspection standard.

Each year, 6.8 million passengers board cruise ships in North America. According to Cruise Lines International Association (CLIA), a nonprofit organization representing 24 cruise lines, the number of North American cruise passengers has increased by 17 percent since 2001.
Health Behavior News Service: 202-387-2829 or
Interviews: Contact CDC Media Relations at 404-639-3286.
American Journal of Preventive Medicine: Contact the editorial office at 619-594-7344;


Center for Advancing Health

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