Patients were excluded from the study if: (a) aged below 3 months or above 24 months; (b) duration of symptoms was 14 days and more; (c) wheezing illness documented; (d) confirmed to have comorbidities related to cardiac diseases, central nervous system diseases, birth defects affecting upper and lower respiratory tract systems such as cleft lip and craniofacial abnormalities, gastroesophageal reflux, or aspiration pneumonitis; (e) premature infants (gestational age <37 completed weeks); and (f) the pneumonia was not confirmed radiologically.