VIRAL LOWER RESPIRATORY TRACT INFECTION IN YEARLY CHILDHOOD AGENTS-EPIDEMIOLOGY

Viral lower respiratory tract infections (LRTIs) in children during their first year of life are predominantly caused by respiratory syncytial virus (RSV), which is the leading epidemiological agent responsible for these infections globally ⁴. Other significant viral agents include influenza viruses, parainfluenza viruses, adenoviruses, human metapneumovirus, and rhinoviruses, but RSV remains the primary pathogen especially in infants under 12 months ⁴[(Li et al., 2022)].

RSV is highly prevalent and is the main cause of bronchiolitis and pneumonia in this age group, contributing substantially to hospital admissions and morbidity worldwide ⁴[(Asseri, 2025)]. The burden of RSV-related acute lower respiratory infections is particularly high in infants younger than 1 year, with seasonal epidemics leading to peaks in disease incidence ⁴[(Li et al., 2022)].

Influenza viruses also contribute to viral LRTIs in infants, though less frequently than RSV, and their impact varies seasonally and geographically ⁵[(Li et al., 2022)]. Other viruses such as parainfluenza and adenoviruses are less common but still recognized causes of LRTIs in this population ⁴[(Asseri, 2025)].

Recent clinical trials and epidemiological studies continue to emphasize RSV as the primary target for preventive interventions, including monoclonal antibodies like nirsevimab, underscoring its dominant role in infant viral LRTIs ⁴[(Arbetter et al., 2025)].