Norovirus disease in the United States

Abstract

Although recognized as the leading cause of epidemic acute gastroenteritis across all age groups, norovirus has remained poorly characterized with respect to its endemic disease incidence. Use of different methods, including attributable proportion extrapolation, population-based surveillance, and indirect modeling, in several recent studies has considerably improved norovirus disease incidence estimates for the United States. Norovirus causes an average of 570-800 deaths, 56,000-71,000 hospitalizations, 400,000 emergency department visits, 1.7-1.9 million outpatient visits, and 19-21 million total illnesses per year. Persons >65 years of age are at greatest risk for norovirus-associated death, and children <5 years of age have the highest rates of norovirus-associated medical care visits. Endemic norovirus disease occurs year round but exhibits a pronounced winter peak and increases by ≤ 50% during years in which pandemic strains emerge. These findings support continued development and targeting of appropriate interventions, including vaccines, for norovirus disease.

Keywords: United States; epidemic acute gastroenteritis; incidence; norovirus; norovirus disease; viruses.

Figure 1

Rates of A) norovirus-associated deaths. B) hospitalizations, C) emergency department (ED) visits, and D) outpatient visits by age group, United States. Data were derived from studies using indirect attribution from regression modeling (–11), attributable proportion extrapolation (2), and laboratory-confirmed population-based surveillance (8). Error bars indicate 95% CIs if reported.

Figure 2

Number of A) norovirus-associated deaths, B) hospitalizations, C) emergency department (ED) visits, and D) outpatient visits across all age groups, by month and year, United States. Data were derived from studies using indirect attribution from regression modeling (–11). Shaded areas indicate years of pandemic strain emergence (2002–2003 and 2006–2007).

Figure 3

Estimates of annual burden (annual number of illnesses and associated outcomes) and individual lifetime risks for norovirus disease across all age groups, United States. Data were derived from estimates of deaths (6,9), hospitalizations (6,10), emergency department visits (13), outpatient visits (7,11), and illnesses (6,7). Ranges represent point estimates from different studies, not uncertainty bounds.