Clinical characteristics and outcomes of respiratory syncytial virus and human metapneumovirus ınfections in children under five years of age.

UNLABELLED: Respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) are major causes of acute respiratory tract infections in young children and share many epidemiological and clinical characteristics. This study aimed to compare the clinical characteristics, outcomes, and healthcare costs associated with RSV and hMPV infections in children younger than five years of age. In this retrospective comparative cohort study, children aged 1-71 months with laboratory-confirmed RSV or hMPV infection identified by multiplex real-time polymerase chain reaction were included. RSV cases identified between September 2022 and April 2023 and hMPV cases identified between September 2022 and December 2025 were included. Both outpatient and hospitalized patients evaluated at a tertiary pediatric hospital were enrolled. A total of 693 children were included, comprising 547 with RSV infection and 146 with hMPV infection. Children with hMPV infection were significantly older and more frequently had underlying comorbidities than those with RSV infection. Bronchiolitis, cough, nasal congestion, tachypnea, chest retractions, rhonchi, oxygen supplementation, inhaled therapies, corticosteroid use, and hospitalization were more common among children with RSV infection (all p < 0.05). In contrast, pneumonia was more frequently observed in the hMPV group (p = 0.015). Lengths of hospital and pediatric intensive care unit stay were comparable between the groups (all p > 0.05).

CONCLUSION: Consistent with previous studies, RSV and hMPV differed in age distribution, clinical presentation, and healthcare utilization. These data provide additional evidence from a tertiary pediatric center in Türkiye and support the generalizability of these observations across different geographic settings.

WHAT IS KNOWN: • RSV and hMPV are major causes of acute respiratory tract infections in young children, but direct comparisons between these viruses remain limited.

WHAT IS NEW: • In this large pediatric cohort, RSV predominantly affected younger children and was associated with more bronchiolitis, hospitalization, and supportive treatment needs, whereas hMPV was more common in older children with comorbidities and was more frequently associated with pneumonia.