Epidemiologic characteristics and clinical outcomes of respiratory syncytial virus in hospitalized care in Lebanon: a prospective observational study.

Introduction: The aim of this study was to describe the epidemiology and clinical outcomes of respiratory syncytial virus (RSV) infection in hospitalized children and adults from a sentinel surveillance network in Lebanon, and to compare the RSV rates and seasonality before and during COVID-19 pandemic. Methods: This study was based on the data from the Lebanese component of the Global Influenza Hospital Surveillance Network (GIHSN) during three consecutive seasons between 2019-2021 at six hospitals, following a standardized protocol based on age-specific criteria. Specimens were tested for RSV. The epidemiologic, clinical, and severity characteristics were analyzed. Descriptive statistics were used to summarize demographics, RSV rate, and outcomes. Univariate analyses were performed using Pearson's Chi-square or Fisher's exact test, and associations were expressed as unadjusted odds ratios (95% CI). A p-value ≤0.05 was considered significant. Results: From January 2019 to September 2021, 2,626 of 7,081 eligible inpatients were enrolled in the study, with 188 tested positives for RSV (7.3%). The majority (74.5%) of RSV-positive subjects were children under 5 years of age, and 9.6% of patients were ≥ 65 years of age. The positivity rate varied across seasons (2.1%-11.1%) (p-value <0.001); the 2020-2021 season -was disrupted by COVID-19 pandemic - recording the lowest rate of 1.1% (p-value <0.001) during the typical winter months followed by an off-season RSV resurgence. Fever, cough, nasal congestion, wheezing, neurological symptoms, diarrhea and decreased oral intake were significantly associated with RSV infection (p < 0.05). Cough and wheezing were predominant in RSV-positive children <5 and adults aged ≥ 65 years. Among RSV-positive subjects, 8% required ICU admission, 5.3% received mechanical ventilation, and 2.7% died. Severe outcomes were more common in those ≥65 years, and the presence of ≥2 comorbidities and underlying cardiovascular disease significantly increased the risks of mechanical ventilation (OR = 7.44 [1.13-48.99], p-value 0.037 and OR = 8.32 [2.20-31.37], p-value 0.004, respectively) and in-hospital death (OR = 22.67 [1.91-268.50], p-value 0.013 and OR = 11.50 [1.82-72.85], p-value 0.016, respectively). Conclusions: This study demonstrates the significant burden of RSV, especially in young infants with or without co-morbidities and in older adults with co-morbidities. Given the recent rollout of RSV vaccines and monoclonal antibodies, continued surveillance is needed to monitor changes in epidemiology, seasonality, and disease burden, especially in low- and middle-income countries.