Epidemiology and Infection

Systematic Review


Norovirus outbreaks: a systematic review of commonly implicated transmission routes and vehicles

E. J. BITLERa1, J. E. MATTHEWSa1, B. W. DICKEYa1, J. N. S. EISENBERGa2 and J. S. LEONa1 c1

a1 Emory University, Atlanta, GA, USA

a2 University of Michigan, Ann Arbor, MI, USA


Causal mechanisms of norovirus outbreaks are often not revealed. Understanding the transmission route (e.g. foodborne, waterborne, or environmental) and vehicle (e.g. shellfish or recreational water) of a norovirus outbreak, however, is of great public health importance; this information can facilitate interventions for an ongoing outbreak and regulatory action to limit future outbreaks. Towards this goal, we conducted a systematic review to examine whether published outbreak information was associated with the implicated transmission route or vehicle. Genogroup distribution was associated with transmission route and food vehicle, but attack rate and the presence of GII.4 strain were not associated with transmission route, food vehicle, or water vehicle. Attack rate, genogroup distribution, and GII.4 strain distribution also varied by other outbreak characteristics (e.g. setting, season, hemisphere). These relationships suggest that different genogroups exploit different environmental conditions and thereby can be used to predict the likelihood of various transmission routes or vehicles.

(Received October 13 2012)

(Revised December 20 2012)

(Accepted January 08 2013)

(Online publication February 22 2013)

Key words

  • Norwalk agent and related viruses;
  • outbreaks;
  • systematic review;
  • transmission;
  • vehicles


c1 Author for correspondence: Dr J. S. Leon, Emory University, Hubert Department of Global Health, Mailstop 1518-002-7BB, 1518 Clifton Road NE, Atlanta, GA 30322, USA. (Email: juan.leon@emory.edu)