Literature Commentary by Dr. John G. Bartlett: Norovirus and Acute Gastroenteritis, January 2008

John G. Bartlett, MD


January 10, 2008

Centers for Disease Control and Prevention (CDC). Norovirus Activity - United States, 2006-2007. MMWR Morb Mortal Wkly Rep. 2007;56:842-846.

Purpose: The report provides an update on norovirus activity for outbreaks that occurred from October 2006 through June 2007. The study investigators emphasize the substantial increase in cases of norovirus that appear to be associated with 2 new GII.4 norovirus variants designated Minerva and Laurens. Some of the specific information provided is summarized below.

Individual State and City Data: Data are provided for North Carolina, Wisconsin, New York state, and Boston, Massachusetts. The data in Table 1 summarize the number of outbreaks of acute gastroenteritis (AGE) for 2005 and 2006 and the number of cases and deaths in 2006.

United States Laboratory Surveillance: During 2006, the National Calicivirus Laboratory at the United States Centers for Disease Control and Prevention (CDC) tested 761 stool specimens from 126 outbreaks and confirmed norovirus in 114 (90%), including 87 (76%) that were associated with the new GII.4 norovirus variants noted. The Minerva variant accounted for 15 of 25 outbreaks on cruise ships in December 2006, and Laurens accounted for 10 of 25 outbreaks in 2006 and 33 of 122 outbreaks in 2007. The totals provided for the United States showed 372 outbreaks of AGE from October through December 2005; this number increased by 254% to 1316 for the same period in 2006. Of these 1316 cases, a total of 382 (29%) had norovirus confirmation by reverse transcription polymerase chain reaction (RT-PCR). An epidemiologic tracing for the past 3 years showed the typical epidemiology of norovirus based on the percentage of emergency department visits for nausea, vomiting, or diarrhea in Boston. As anticipated, there was an increase in the percentage of AGE cases attributed to norovirus from December to May, with a low of approximately 2.5% and a peak of approximately 9%.

Outbreak Settings: Table 2 provides a perspective on the wide range of outbreak settings in which AGE has been attributed to norovirus in 2006.

Prevention: The following lists some of the recommended procedures to prevent norovirus transmission:

  • Hand hygiene with alcohol-based hand gels;

  • Disinfection of contaminated surfaces with a 1:10-50 dilution of chlorine bleach;

  • Do not return to work or school for 24 to 72 hours after symptoms resolve;

  • During outbreaks, use contact precautions. Avoid sharing staff members between units or facilities with affected patients, cluster symptomatic patients, instruct visitors on hand hygiene, and close affected units to new admissions and transfers, and

  • For further information see and

Comment: Norovirus is now recognized as the dominant cause of outbreaks of AGE in the United States. This generally causes a self-limited bout of vomiting or diarrhea, usually as a result of contaminated food. However, this report includes several deaths resulting from acute disease, primarily in elderly patients who were presumably quite fragile. The diversity of settings is of interest. The dominant season for norovirus infection is winter, hence the term "winter vomiting disease." The organism has been known for many decades, but the ability to make the diagnosis and more clearly define the epidemiology is now readily available with RT-PCR.


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