Human Metapneumovirus Versus Respiratory Syncytial Virus in the Pediatric Emergency Department: Inflammatory Indices, Cycle‐Threshold Profiles and Outcomes

Inflammatory‐biomarker, cycle‐threshold (Ct) and co‐detection data on human metapneumovirus (hMPV) in the pediatric emergency department remain scarce. We retrospectively studied 203 children with multiplex RT‐PCR–confirmed respiratory virus positivity at a tertiary pediatric emergency department (January–May 2025). Inflammatory indices, C‐reactive protein (CRP) and per‐target Ct were compared between hMPV and RSV; predictors of antibiotic prescribing were assessed by ROC and multivariable regression. hMPV (17.7%) and RSV (28.6%) were dominant detections; co‐detection 24.1%. Compared with RSV, hMPV affected older children with higher comorbidity, more pneumonia and neutrophil‐driven inflammation (neutrophil‐to‐lymphocyte ratio [NLR], systemic immune‐inflammation index [SII], CRP higher; p  ≤ 0.006). Dominant Ct differed across pathogens (Kruskal–Wallis p  < 0.001); rhinovirus carried the lowest viral load. Paired non‐dominant Ct exceeded dominant Ct (median ΔCt +3.6, p  = 0.013). CRP independently predicted antibiotic prescribing (AUC 0.78, cut‐off 3.9 mg/L). hMPV showed a neutrophil‐dominant inflammatory phenotype in older, more comorbid children than RSV. Per‐target Ct supports the lowest‐Ct‐dominant convention. CRP—not white‐cell indices—drove antibiotic prescribing; a 3.9 mg/L cut‐off supports stewardship in PCR‐confirmed pediatric viral respiratory infection.