Incidence of Norovirus-Associated Acute Gastroenteritis in Four Veteran's Affairs Medical Center Populations in the United States, 2011–2015. (4th October 2017) - Grytdal, Scott
Abstract: Background: In the USA, norovirus is an important cause of epidemic acute gastroenteritis (AGE) as well as a leading cause of pediatric AGE. However, the burden of sporadic norovirus disease in US adults has not been well-documented. Our objective was to estimate the incidence of outpatient visits and hospitalizations for community-acquired norovirus AGE at four Veterans Affairs Medical Centers (VAMCs) and their associated outpatient clinics in Atlanta, GA; Bronx, New York; Houston, TX; and Los Angeles, CA. Methods: From November 2011 to September 2015, stool specimens collected for clinician-requested diagnostic testing within 7 days of AGE symptom onset and with reported vomiting or diarrhea were tested for norovirus by real-time RT-PCR and positive samples were genotyped by Sanger sequencing. Incidence of norovirus-associated outpatient visits and hospitalizations were calculated by multiplying the prevalence of norovirus among tested specimens by AGE-coded outpatient encounters and inpatient discharges, and dividing by the unique patients served at each VAMC. Results: 1, 620 stool specimens were tested from all 4 sites. Seven percent of outpatient ( n = 795) samples (annual range: 3%–10%; range by site: 3%–10%) and 6% of ( n = 825) samples from hospitalized patients tested positive for norovirus (annual range: 3%–8%; range by site: 3%–10%). Forty-four percent of norovirus-positive specimens were typed as GII.4 Sydney. Seventy-four percent of norovirus-positive specimens were collected between November and April. From 2011 to 2015, outpatient norovirus incidence was 250/100, 000 population (annual range: 129 to 426/100, 000; range by site: 87 to 428/100, 000), and the incidence of norovirus hospitalizations was 28/100, 000 population (annual range: 19 to 39/100, 000; range by site: 14 to 57/100, 000). By age group and setting, the highest incidence was observed among 45- to 64-year-old outpatients (370/100, 000 population), and 85+-year-old inpatients (63/100, 000 population). Conclusion: This study provides estimates of the incidence of norovirus AGE outpatient visits and hospitalizations across multiple years among a geographically distributed VA population, highlighting the substantial burden of norovirus in US adults. Disclosures: All authors: No reported disclosures.