1305. Impact and clinical significance of the emergent norovirus GII.4 Sydney strain United States, 20122013
Session: Poster Abstract Session: Below the Diaphragm
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
  • Poster-Leshem-IDWeek-3-revised-2FINAL.pdf (552.3 kB)
  • Background:

    Noroviruses are the leading cause of epidemic gastroenteritis in the United States (US); most outbreaks are caused by GII.4 strains. Over the past decade, new GII.4 strains have emerged every 2–3 years and have sometimes led to increased outbreak activity. In 2012, global detection of a new norovirus strain, GII.4 Sydney, raised concerns about its potential impact in the US.


    We analyzed norovirus outbreaks reported in five states (Minnesota, Ohio, Oregon, Tennessee, and Wisconsin) and emergency department visits for gastrointestinal illness in one state (Ohio) during the 2012–2013 season and compared with previous two seasons. 


    During August 1st 2012–February 27th2013, 503 norovirus outbreaks were reported compared with 446 and 387 in 2011–2012 and 2010–2011 during the same period, respectively.  There was considerable variation between the states, with an increased cumulative number of outbreaks in three states (Oregon, Tennessee, and Ohio) while two states (Wisconsin and Minnesota) reported a decrease.

    Of 270 outbreaks with sequence data, 160 (59%) were caused by GII.4 Sydney; the proportion of GII.4 Sydney outbreaks increased from 8% in September, 2012 to 85% in February 2013 (chi-square for trend; p<0.0001). There was no significant difference in the proportion of GII.4 Sydney outbreaks between the states with an increased cumulative number of outbreaks in 2012–13 compared with those that had a decrease (58% versus 62%, respectively; p=0.5). The increase in gastrointestinal emergency department visits was similar during the 2012–2013 season when compared with previous seasons.

    Compared with non-GII.4 Sydney outbreaks, GII.4 Sydney outbreaks occurred more frequently in healthcare settings (43% vs. 75%, rate ratio 1.7; 95% CI=1.4-2.2) and affected a greater proportion of patients over 50 (43% vs. 60%, rate ratio 1.4; 95% CI=1.3-1.6).


    GII.4 Sydney has become the predominant US norovirus outbreak strain during the 2012-2013 season; however, its emergence does not appear to have caused a substantial increase in outbreak activity compared with previous seasons. Proper hand hygiene, environmental disinfection, and isolation of ill persons remain the mainstays of norovirus prevention and control.

    Eyal Leshem1, Mary Wikswo1, Leslie Barclay1, Eric Brandt2, William Storm2, Ellen Salehi3, Traci Desalvo4, Tim Davis5, Amy Saupe6, Ginette Dobbins6, Hillary A. Booth7, Christianne Biggs8, Katie Garman9, Amy Woron9, Umesh D. Parashar, MBBS, MPH1, Jan Vinje, PhD1 and Aron J. Hall, DVM, MSPH1, (1)Centers for Disease Control and Prevention, Atlanta, GA, (2)Ohio Department of Health, Columbus, OH, (3)Ohio Dept. of Health, Columbus, OH, (4)Bureau of Communicable Diseases & Emergency Response, Wisconsin Division of Public Health, Madison, WI, (5)Wisconsin State Laboratory of Hygiene, Madison, WI, (6)Minnesota Department of Health, St. Paul, MN, (7)Oregon Public Health Division, Portland, OR, (8)Oregon State Public Health Laboratory, Portland, OR, (9)Tennessee Department of Health, Nashville, TN


    E. Leshem, None

    M. Wikswo, None

    L. Barclay, None

    E. Brandt, None

    W. Storm, None

    E. Salehi, None

    T. Desalvo, None

    T. Davis, None

    A. Saupe, None

    G. Dobbins, None

    H. A. Booth, None

    C. Biggs, None

    K. Garman, None

    A. Woron, None

    U. D. Parashar, None

    J. Vinje, None

    A. J. Hall, None

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