Risk of Hospitalization and Mortality Following Medically Attended Norovirus Infection-Veterans Health Administration, 2010-2018.

Background: While prior studies have suggested a role for norovirus gastroenteritis in contributing to severe morbidity and mortality, the importance of norovirus as a causal pathogen for hospitalization and mortality remains poorly understood. We estimated the effect of laboratory-confirmed norovirus infection on hospitalization and mortality among a national cohort of veterans who sought care within the Veterans Affairs health care system.

Methods: We analyzed electronic health record data from a cohort study of adults who were tested for norovirus within the Veterans Affairs system between 1 January 2010 and 31 December 2018. Adjusted risk ratios (aRRs) for hospitalization and mortality were estimated using log-binomial regression models, adjusting for age, , underlying medical conditions, and nursing home residence.

Results: In total, 23 196 veterans had 25 668 stool samples tested for norovirus; 2156 samples (8.4%) tested positive. Testing positive for norovirus infection, compared with testing negative, was associated with a slight increased risk of hospitalization (aRR, 1.13 [95% confidence interval, 1.06-1.21]) and a significant increased risk of mortality within 3 days after the norovirus test (2.14 [1.10-4.14]). The mortality aRR within 1 week and 1 month were reduced to 1.40 (95% confidence interval, .84-2.34) and 0.97 (.70-1.35), respectively.

Conclusions: Older veterans with multiple comorbid conditions were at a slight increased risk of hospitalization and significant increased risk of mortality in the 3 days after a norovirus-positive test, compared with those testing negative. Clinicians should be aware of these risks and can use these data to inform clinical management for veterans with norovirus.