Outbreaks of acute gastroenteritis on cruise ships and on land: identification of a predominant circulating strain of norovirus - United States 2002

Marc-Alain Widdowson, Elaine H Cramer, Leslie Hadley, Joseph S Bresee, R. Suzanne Beard, Sandra N Bulens, Myrna Charles, Wairimu Chege, Elmira Isakbaeva, Jennifer G Wright, Eric Mintz, David Forney, Jeffrey Massey, Roger I Glass, Stephan S Monroe

In 2002, a sharp increase in outbreaks of norovirus-associated illness on cruise ships and on land encouraged us to examine the molecular epidemiology of detected noroviruses to identify a common strain or source. Of 14 laboratory-confirmed outbreaks aboard ships, 86% (12) were attributed to caliciviruses. Outbreak characteristics included continuation on successive cruises in 50%, multiple modes of transmission in 58% and high (>10%) attack rates in 58% . 7 (64%) outbreaks were attributed to a previously unreported lineage of norovirus, provisionally named Farmington Hills strain. From May through December 2002, 10 (45%) of 22 land-based outbreaks were attributed to this strain. Sequence analysis provided insights into norovirus transmission by documenting links between outbreaks, introductions of strains aboard ships and viral persistence onboard despite cleaning. Control measures for outbreaks should address all routes of transmission. Better outbreak surveillance and sequence data collection will help monitor norovirus strains and identify common sources.

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