Influenza B virus outbreak on a cruise ship--Northern Europe, 2000.

During June 23-July 5, 2000, an outbreak of respiratory illnesses occurred on the MS Rotterdam (Holland America Line & Windstar Cruises) during a 12-day Baltic cruise from the United Kingdom to Germany via Russia. The ship carried 1311 passengers, primarily from the United States, and 506 crew members from many countries. Although results of rapid viral testing for influenza A and B viruses were negative, immunofluorescence staining and viral culture results implicated influenza B virus infection as the cause of the outbreak. This report summarizes the findings of the outbreak investigation conducted by the ship's medical department and describes the measures taken to control the outbreak. Travelers at high risk for complications of influenza who were not vaccinated with influenza vaccine during the preceding fall or winter should consider receiving influenza vaccine before travel with large tourist groups at any time of year or to certain regions of the world.