Outbreaks of Acute Gastroenteritis on Cruise Ships and on Land: Identification of a Predominant Circulating Strain of Norovirus—United States, 2002

Authors:
  • ECElaine H. Cramer
    Elaine H. Cramer
  • LHLeslie Hadley
    Leslie Hadley
  • JBJoseph S. Bresee
    Joseph S. Bresee
  • RBR. Suzanne Beard
    R. Suzanne Beard
  • SBSandra N. Bulens
    Sandra N. Bulens
  • MCMyrna Charles
    Myrna Charles
  • WCWairimu Chege
    Wairimu Chege
  • EIElmira Isakbaeva
    Elmira Isakbaeva
  • JWJennifer G. Wright
    Jennifer G. Wright
  • EMEric Mintz
    Eric Mintz
  • DFDavid Forney
    David Forney
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Abstract
In 2002, a sharp increase in outbreaks of norovirus-associated illness, both 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 on cruise ships, 12 (86%) were attributed to caliciviruses; among these 12, outbreak characteristics included continuation on successive cruises in 6 (50%), multiple modes of transmission in 7 (58%), and high (>10%) attack rates in 7 (58%). Eleven of the 12 calicivirus outbreaks were attributed to noroviruses, 7 (64%) of which were attributed to a previously unreported lineage, provisionally named "the Farmington Hills strain." From May 2002 to December 2002, 10 (45%) of 22 land-based outbreaks also were attributed to this strain. Nucleotide-sequence analysis provided insights into norovirus transmission, by documenting links among outbreaks, the introduction of strains onto ships, and viral persistence on board (despite cleaning). Control measures for outbreaks should address all routes of transmission. Better outbreak surveillance and collection of data on sequences will help to monitor norovirus strains and to identify common sources.