Respiratory viral infections and disease severity in hospitalized children: A preimmunoprophylaxis baseline study highlighting the role of human metapneumovirus

BACKGROUND: With the introduction of respiratory syncytial virus (RSV) immunoprophylaxis, the contribution and severity of other respiratory viruses require a more comprehensive investigation in different patient cohorts. METHODS: We performed a retrospective study of hospitalized children with laboratory-confirmed respiratory viral infections at a tertiary pediatric center between the years 2018 and 2024. Clinical characteristics, outcomes, and predictors of severe disease were analyzed. RESULTS: Of 35,943 respiratory specimens, 16,866 (46.9%) tested positive for at least one virus. Clinical data from 2424 hospitalized children were analyzed. RSV primarily affected infants (median age 5 months, IQR 2-29), whereas human metapneumovirus (hMPV) and influenza virus (IFV) affected older children (median 26 months, IQR 8-54, and 57 months, IQR 23-108; P < 0.001). Respiratory support was required in 71% of RSV and hMPV cases vs 46% of IFV (P < 0.001). Pediatric intensive care unit admission occurred in 33/352 (9%) of RSV cases, 9/66 (14%) of hMPV cases, and 33/301 (11%) of influenza cases (P > 0.05). In adjusted analyses, RSV was associated with higher odds ratios (OR) of requiring respiratory support (OR 6.20, 95% confidence intervals [CI] 4.60-8.85), followed by hMPV (OR 5.90, 95% CI 3.42-11.7). These associations were stronger than those observed for influenza (OR 2.78, 95% CI 2.07-3.92) and parainfluenza viruses (OR 3.15, 95% CI 2.06-5.13). CONCLUSION: RSV remains the leading cause of severe respiratory disease in early childhood, but hMPV is a substantial contributor in older children with comparable severity and should be considered in future prevention strategies.