215. Role of Norovirus Gastroenteritis in the Ambulatory Setting — United States, 2001-2009
Session: Poster Abstract Session: Epidemiology of Enterics Pathogens
Thursday, October 18, 2012
Room: SDCC Poster Hall F-H

Gastroenteritis remains an important cause of morbidity in the US, most being of undetermined etiology. Norovirus is the leading cause of epidemic gastroenteritis, but its contribution to ambulatory endemic gastroenteritis is unknown, due to lack of widely available diagnostics.

Methods: Using MarketScan (insurance claim) databases, cause-specified and cause-unspecified gastroenteritis coded emergency department (ED) and outpatient visits were extracted for July 2001 to June 2009. Using cause-specified encounters, time-series regression models were fitted to predict the number of unspecified gastroenteritis due to specific pathogens other than norovirus. After removing specific pathogens, background, and secular trends, model residuals were used to estimate norovirus visits, by subtracting the minimum monthly residual for each seasonal year from each monthly residual.

Results: From 2001–2009, an annual mean of 938,994 visits (501 visits per 10,000 persons) due to cause-unspecified gastroenteritis occurred, representing 95% of all-cause gastroenteritis. The annual mean rate of norovirus-associated ED and outpatient visits was 14 and 57 cases per 10,000 persons, respectively, across all age-groups. Rates were higher during known norovirus epidemic seasonal years 2002/03 and 2006/07: 25 and 16 ED, and 57 and 81 outpatient visits per 10,000 persons, respectively. Rates for age groups 0–4, 5–17, 18–64, and ≥65 years, were 40, 10, 12, and 15 ED, and 223, 85, 35, and 55 outpatient visits per 10,000 persons, respectively. Norovirus was estimated to cause 13% of all gastroenteritis and 51% of norovirus visits occurred from November to February. Norovirus contributed to an estimated 400,000 ED visits, and 1.7 million office visits, annually, across all ages.

Conclusion: Norovirus is a substantial cause of diarrheal disease in the ambulatory setting, exhibits winter seasonality, and surges with emergence of new strains. These findings support development of rapid diagnostics and vaccines.

Paul Gastanaduy, MD, MPH, Aron J. Hall, DVM, MSPh, Aaron T. Curns, MPH, Umesh D. Parashar, MBBS, MPH and Ben A. Lopman, MSc, PhD, Centers for Disease Control and Prevention, Atlanta, GA


P. Gastanaduy, None

A. J. Hall, None

A. T. Curns, None

U. D. Parashar, None

B. A. Lopman, None

Findings in the abstracts are embargoed until 12:01 a.m. PST, Oct. 17th with the exception of research findings presented at the IDWeek press conferences.