Emerging Infectious Diseases
Volume 16, Number 11–November 2010
http://www.cdc.gov/ncidod/EID/index.htm

Research
Outbreaks of Pandemic (H1N1) 2009 and Seasonal Influenza A (H3N2) on Cruise Ship
Kate A. Ward, Paul Armstrong, Jeremy M. McAnulty, Jenna M. Iwasenko, and Dominic E. Dwyer
Author affiliations: New South Wales Health, Sydney, New South Wales, Australia (K.A. Ward, J.M. McAnulty); Western Australian Department of Health, Perth, Western Australia, Australia (P. Armstrong); South Eastern Area Laboratory Services, Sydney (J.M. Iwasenko); and Institute of Clinical Pathology and Medical Research, Sydney (D.E. Dwyer)

Abstract
To determine the extent and pattern of influenza transmission and effectiveness of containment measures, we investigated dual outbreaks of pandemic (H1N1) 2009 and influenza A (H3N2) that had occurred on a cruise ship in May 2009. Of 1,970 passengers and 734 crew members, 82 (3.0%) were infected with pandemic (H1N1) 2009 virus, 98 (3.6%) with influenza A (H3N2) virus, and 2 (0.1%) with both. Among 45 children who visited the ship’s childcare center, infection rate for pandemic (H1N1) 2009 was higher than that for influenza A (H3N2) viruses. Disembarked passengers reported a high level of compliance with isolation and quarantine recommendations. We found 4 subsequent cases epidemiologically linked to passengers but no evidence of sustained transmission to the community or passengers on the next cruise. Among this population of generally healthy passengers, children seemed more susceptible to pandemic (H1N1) 2009 than to influenza (H3N2) viruses. Intensive disease control measures successfully contained these outbreaks.