3.1-Study population
We evaluated 7278 respiratory specimens during the study period. Afterward, we reviewed the patients’ medical records and included 2115 (29.2%) children in the study. Of these, mild and severe LRTI were observed in 562 (26.6%) and 1553 (73.4%) children, respectively. Seven hundred ninety-five (10.9%) patients with a diagnosis other than LRTI, 2200 (30.2%) not fulfilled criteria of LRTI according to WHO guideline, 834 (11.4%) with hospital-acquired viral LRTI, 212 (2.9%) with a primary bacterial infection, and 1074 (14.8%) with a secondary bacterial infection were excluded from the study (Figure 1). Overall, the most common detected viruses were RSV (906; 42.8%) and HRV (733; 34.7%), followed by HBoV (212; 10.0%). We identified that HRV (226; 40.2% vs. 507; 32.6%; P = .001), influenza A (73; 13.0% vs. 136; 8.8%; P = .004), and PIV3 (47; 8.4% vs. 84; 5.4%;P = .01; Supplemental Table S1) were observed more frequently in severe disease compared with mild disease.