2327. 2018–2019 Seasonal Epidemiology of Infections Caused by Influenza Viruses and RSV in Ecuadorean Children Less than 5 Years of Age Residing at Opposite Extremes of Elevation

BACKGROUND: The epidemiology of ambulatory acute respiratory tract infections (ARTI) caused by influenza viruses and respiratory syncytial virus (RSV) in young children is not well described in Ecuador. The seasonality of these infections vary across and within tropical countries experiencing different climates. Understanding trends that differ from one region to the next is needed to optimize implementation of effective preventive measures. METHODS: This 5-year prospective study compares the epidemiology of ARTI caused by influenza and RSV in children from Machala (6 m) and Quito (2,832 m), Ecuador. Children < 5 years presenting with ARTI for ≤7 days are eligible. Demographic and clinical data are gathered and a nasopharyngeal sample is collected for diagnostic testing using the Biofire FilmArray® respiratory panel platform that allows for the detection of 17 viruses. RESULTS: Between July 2018 and March 2019, we enrolled 446 subjects; 322 from Machala and 124 from Quito. Eighteen percent of the samples from Quito and 9% from Machala were positive for influenza viruses, while RSV accounted for 4% of the samples from Quito and 5% of those from Machala. The influenza B season at both elevations lasted 14 weeks, but started 5 weeks earlier in Machala (weeks 29–42 vs. weeks 34–47). Influenza B seasonal activity preceded influenza A at both sites. In Machala, the influenza A season began 6 weeks after the influenza B season (weeks 48–4), but overlapped with the influenza B season in Quito (weeks 45–2). In Machala, RSV was detected during the first week of surveillance (2018, week 29) but did not re-emerge to cause sustained activity until 2019, week 6. The RSV season began in Quito in 2018 during week 47, with sustained activity through the time of this report, 2019, week 12. CONCLUSION: The 2018–2019 seasonal epidemiology of ARTI caused by influenza viruses and RSV differed between Ecuadorean children living close to sea level and those living at high elevation. Patterns of seasonal activity observed throughout the 5-year study period will facilitate decision-making regarding the optimal timing and duration for implementing existing and emerging prevention measures. DISCLOSURES: All authors: No reported disclosures.