Respiratory Syncytial Virus Seasonality and Disease Severity Among Children Under 5 in Atlanta, Georgia, United States, 2018-2023.

Background: The coronavirus disease 2019 (COVID-19) pandemic had dramatic impacts on the epidemiology of respiratory syncytial virus (RSV). We used surveillance data collected by the Georgia Emerging Infections Program to investigate seasonality and severity of RSV pre- versus postpandemic in children under 5 years old in Atlanta, Georgia. Method: We analyzed 3282 RSV-associated hospitalizations of children under 5 years old residing in the Atlanta area from 2018 to 2023. There were 4 distinct waves of RSV hospitalizations: 2 prepandemic and 2 postpandemic. Using regression modeling, we assessed the impact of wave on the length of hospital stay and intensive care unit (ICU) admission among all hospitalizations and on the length of ICU stay and mechanical ventilation among ICU admissions. Results: The 2 postpandemic waves of RSV-associated hospitalizations fell outside of the typical viral respiratory season in the northern hemisphere, seemingly delayed by COVID-19-associated disruptions in transmission. Age at hospitalization and race/ethnicity differed significantly across all waves, with age increasing over time. Regression models for all hospitalizations showed a statistically significant reduction in severity (shorter length of hospital stay and lower risk of ICU admission) postpandemic after adjustment for age and race/ethnicity. Analysis of ICU admissions adjusted for age, race/ethnicity, and underlying medical conditions tended toward shorter ICU stays and lower risk of mechanical ventilation postpandemic, although these findings did not show statistical significance. Conclusions: The COVID-19 pandemic delayed the expected annual seasonality of RSV in children under 5, and the delayed peaks of hospitalizations consisted of, on average, less severe disease than prepandemic.