HHV-7 positivity in hospitalized children with acute respiratory tract infections: co-detection patterns and clinical outcomes

To analyze the epidemiology, co-detection patterns, and clinical features associated with Human Herpesvirus 7 (HHV-7) positivity in children with acute respiratory tract infections (ARTIs). We retrospectively analyzed 9,521 pediatric inpatients with ARTIs using targeted next-generation sequencing (tNGS) to detect HHV-7 and co-detected microbes. False discovery rate (FDR) correction (Benjamini–Hochberg procedure), age-matched sensitivity analysis, and multivariable logistic regression were applied to control for multiple testing and confounding. The overall HHV-7 detection rate was 3.3% (315/9,521; median age: 5 years) with an extremely high co-detection rate (99.0%), predominantly Streptococcus pneumoniae (32.1%), rhinovirus (30.8%), EBV (30.5%), and Mycoplasma pneumoniae (30.2%). Bronchial wall thickening (81.1%) and ground-glass opacities (74.8%) were main CT findings. Notably, a subset of patients exhibited substantial clinical severity, with 16.8% (53/315) requiring respiratory support and 4.8% (15/315) admitted to the ICU. Regarding discharge outcomes, in-hospital mortality was zero, with 96.8% (305/315) achieving clinical recovery, while 3.2% (10/315) underwent voluntary discharge prior to full recovery. Although HHV-7-positive children (without CMV co-detection) initially presented with lower unadjusted respiratory support rates than CMV-positive children without HHV-7 co-detection (16.5% vs. 38.7%; FDR-adjusted q < 0.001), this difference lost significance in age-matched sensitivity analysis ( q > 0.05). Multivariable logistic regression confirmed that HHV-7 positivity was not independently associated with respiratory support (aOR = 0.57, P = 0.081). Younger age (aOR = 0.98, P < 0.001), elevated procalcitonin (aOR = 1.26, P = 0.047), and non-respiratory specimens (aOR = 5.19, P = 0.026) were identified as independent risk factors, whereas autumn admission was protective (aOR = 0.60, P = 0.045). HHV-7 exhibits a low detection rate (3.3%) in pediatric ARTIs. The high co-detection rate (99.0%) suggests that HHV-7 positivity commonly occurs within polymicrobial respiratory infection contexts; its independent clinical contribution remains uncertain. Baseline clinical severity disparities between HHV-7 and CMV cohorts are primarily driven by host age rather than intrinsic viral pathogenicity.