2507. Active Norovirus Surveillance in Children Under 5 Years With Diarrhea Following Rotavirus Vaccine Introduction in Argentina

BACKGROUND: Acute diarrhea is one of the main causes of infant mortality. Argentina introduced massive rotavirus vaccination in 2015. This introduction in several countries, has changed the distribution of enteropathogens and has been described a decrease in the rotavirus prevalence at the expense of an increase in norovirus (NoV) activity. NoV is reported to be emerging as one of the main agents producing acute diarrhea in the community. In Argentina, there are few experiences estimating its prevalence in cases of acute diarrhea in children. The aim of this study was to analyze the role of NoV in outpatient children <5 years of age with acute diarrhea and their epidemiological pattern. METHODS: Prospective, cross-sectional study of outpatients <5 years attended for acute diarrhea in Children’s Hospital “R. Gutiérrez” between June 2017 and March 2018. Active epidemiological surveillance was performed with a specific case reporting form. Stool samples were collected and tested for NoV (RT-qPCR), clinical and epidemiological data were recorded. RESULTS: A total of 136 patients were included and 125 stools were processed. The median of age was 20 months (IQR: 12–31) and 59% were male; the most common symptom was fever and vomits in 70% and 55%, respectively. A 55% had watery diarrhea and 43% mucohaemorrhagic diarrhea. The severity of the diarrhea (Vesikary Scale) was moderate; 54% (n = 73) and 97% of patients were normohydrated; 24% had a household member with diarrhea. Analyzing vaccination history, 74% had received rotavirus vaccine, 89% of them with 2 doses. From 125 samples tested, 29% (n = 36) were NoV positive and, comparing with the negative cases, were younger (19 vs. 22 months; P < 0.001) and were associated with higher prevalence of rotavirus vaccination (91% vs. 65%; P = 0.004). No statistically difference was found in gender, clinical presentation or severity. CONCLUSION: NoV was detected at high frequencies (29%) presenting moderate acute diarrhea, mainly in children that received rotavirus vaccine. Regarding sporadic acute diarrhea cases in children, it is important to consider the role of NoV as a frequent etiological agent. Further surveillance studies at larger populations are needed to elucidate the prevalence, clinical manifestations and risk factors associated with NoV diarrhea in children. DISCLOSURES: All authors: No reported disclosures.