Incidence of Norovirus-Associated Acute Gastroenteritis across Age Groups in a Peruvian Andean Community.

Norovirus is the leading cause of acute gastroenteritis (AGE) globally. Few longitudinal studies have assessed norovirus-associated AGE incidence across age groups in community settings in Latin America. During April 2015-April 2019, active surveillance for AGE among community members of all ages was conducted through household visits two to three times per week in San Jeronimo, Cusco, Peru. An asymptomatic control household was selected for every fifth AGE case. Stool specimens were collected from AGE cases, asymptomatic household members, and control household members, and they were tested for norovirus using real-time reverse transcriptase polymerase chain reaction. Data on illness characteristics were collected from AGE cases during a 15-day follow-up period. Annual means of 247 households and 1,555 participants were enrolled during each April-March surveillance year, accounting for 4,176 person-years (PY) of observation. Of 1,099 AGE events reported, 1,014 stool specimens were tested, and 186 (18%) were norovirus positive. Norovirus AGE incidence was 4.4/100 PY (95% CI: 3.9-5.1); incidence was highest among those younger than 2 years old (60.9/100 PY; 95% CI: 46.8-79.4). Among 672 stool specimens from asymptomatic controls, 56 (8%) tested positive for norovirus. Odds of norovirus detection were significantly higher among cases compared with controls (odds ratio: 2.2; 95% CI: 1.6-3.1). Age-stratified norovirus incidence in this periurban community aligns with previously published estimates and was highest among those younger than 2 years old. Establishing baseline norovirus incidence in specific communities is crucial to identify target populations and assess effectiveness of future interventions, such as vaccines.