1491. Active Norovirus Surveillance in Children Under 5 Years with Diarrhea after Rotavirus Vaccine Introduction in Argentina (2017–2019)

Background Acute diarrhea is one of the leading causes of infant morbidity and mortality. Argentina introduced massive rotavirus vaccination in 2015. In several countries, this introduction has changed the distribution of enteropathogens. The decrease in the prevalence of rotavirus has been described at the expense of an increase in Norovirus (NoV) activity worldwide. The aim of this study was to analyze the role of NoV in acute diarrhea cases in outpatient children under 5 years of age and their epidemiological profile. Methods A prospective and cross-sectional study in <5 years outpatients attended for acute diarrhea in Children’s Hospital “Dr. Ricardo Gutiérrez” in Buenos Aires, Argentina, between July 2017 and March 2019 was conducted. Active epidemiological surveillance was performed with a specific case reporting form. Stool samples were tested for NoV (RT-qPCR). Clinical and epidemiological data were recorded. Results A total of 252 patients were enrolled and 235 stools samples were tested. Median of age was 22.3 months (IQR: 11–30), 58.7% were male. The most frequent symptoms were fever and vomiting in 63.1% and 53%, respectively; 52% had watery diarrhea, 45.2% had moderate diarrhea according to Vesikari Scale, 95.6% were normohydrated and 22% had a household member with diarrhea. There were no immunocompromised children. A 72% had received rotavirus vaccine, 86% of them with full scheme. From samples tested, 27% (n = 63) were NoV positive. NoV was found throughout the year and the frequency of detection was higher in January and June (summer and winter in Argentina). Regarding genetic diversity the most frequent genogroup was GII (65%; 41/63) and genotype GII.P16-GII.4 Sydney (48%; 20/41). Bacterial co-infection was observed in 35%. Compared with negative cases, NoV were younger (18 vs. 20 months; P < 0.001) and were associated with higher prevalence of rotavirus vaccination (88% vs. 66%; P = 0.001). No statistically difference was found regarding to gender, clinical outcome and severity. Conclusion NoV was detected at high frequency (27%) in children presenting moderate acute diarrhea, mainly in those who received rotavirus vaccine. Regarding sporadic acute diarrhea cases in children, it is important to consider NoV as a frequent etiological agent. Disclosures All authors: No reported disclosures.