Passenger behaviors during norovirus outbreaks on cruise ships.

BACKGROUND Norovirus causes a majority of outbreaks of gastrointestinal (GI) illness on cruise ships calling on the United States. Control measures include patient isolation, hand washing, and facility closure. Little is known about the behaviors and practices of people who have become ill with norovirus GI illness compared to those who remained well during an outbreak. METHODS Passenger surveys were distributed during three cruise ship outbreaks caused by norovirus. Surveys inquired about illness symptoms, ill contacts, illness reporting status, hand sanitation beliefs and practices, and availability of public hand sanitizer. A case was a passenger reporting three or more episodes of loose stool in a 24-hour period, three or more episodes of vomiting in a 24-hour period, or one or more episodes each of loose stool and vomiting in a 24-hour period. Controls reported that they were not ill during the cruise. RESULTS In total, 1,323 responses were compared. All ships had passengers who were ill prior to embarkation. Most cases delayed or did not report their illness to the ship's infirmary because they did not believe it was serious (43%-70% of responses). Cases were less likely to believe that isolation was effective in preventing disease spread [Mann-Whitney-Wilcoxon (MWW) p value <0.0001]. Cases were less likely to believe that hand washing or hand sanitizer are effective means of preventing disease spread (MWW p values 0.002 and 0.04, respectively), wash their hands after restroom use (MWW p value 0.02), or believe that hand sanitizer was available for public use prior to/after knowing about an outbreak (MWW p values 0.002 and 0.03, respectively). CONCLUSIONS Prevention and control of norovirus GI illness may be improved by routine screening of embarking passengers, education about GI illness and its impact on public health, a focus on improving hand-washing practices, and identification of public hand sanitizer dispensing locations.