Increasing Rates of Gastroenteritis Hospital Discharges in US Adults and the Contribution of Norovirus, 1996-2007

Background. Diarrhea remains an important cause of morbidity, but until the mid 1990s, hospital admissions for diarrhea in the US adult population were declining. We aimed to describe recent trends in gastroenteritis hospitalizations and to determine the contribution of norovirus. Methods. We analyzed all gastroenteritis-associated hospital discharges during 1996-2007 from a nationally representative data set of hospital inpatient stays. Annual rates of discharges by age were calculated. Time-series regression models were fitted using cause-specified discharges as explanatory variables; model residuals were analyzed to estimate norovirus- and rotavirus-associated discharges. We then calculated the annual hospital charges for norovirus-associated discharges. Results. Sixty-nine percent of all gastroenteritis discharges were cause-unspecified and rates increased by >= 50% in all adult and elderly age groups (>= 18 years of age) from 1996 through 2007. We estimate an annual mean of 71,000 norovirus-associated hospitalizations, costing $493 million per year, with surges to nearly 110,000 hospitalizations per year in epidemic seasons. We also estimate 24,000 rotavirus hospitalizations annually among individuals aged >= 5 years. Conclusions. Gastroenteritis hospitalizations are increasing, and we estimate that norovirus is the cause of 10% of cause-unspecified and 7% of all-cause gastroenteritis discharges. Norovirus should be routinely considered as a cause of gastroenteritis hospitalization.