High prevalence and clinical impact of microbial co-detection in hospitalized children with human parainfluenza virus type 1

ABSTRACT Human parainfluenza virus type 1 (HPIV-1) is an important but underrecognized pathogen associated with acute respiratory infections (ARI) in children, although its clinical impact remains poorly defined, particularly with microbial co-detection. This study enrolled hospitalized children with ARI who underwent targeted next-generation sequencing (tNGS). Clinical features were compared between HPIV-1 mono-detection and co-detection groups, as well as between patients with severe and non-severe pneumonia. Among 9,394 enrolled children, HPIV-1 was detected in 1.7%, predominantly in those aged 6 months to 2 years. Co-detection with other respiratory pathogens was observed in 95.7% of HPIV-1-positive cases, with viral-bacterial co-infection being the most common pattern. Haemophilus influenzae , Streptococcus pneumoniae , rhinovirus, and Mycoplasma pneumoniae were the most frequently co-detected agents. Compared to the mono-detection group (mostly infants ≤12 months), children with co-detection were older, exhibited higher total immunoglobulin levels, experienced longer hospitalizations, and incurred greater treatment costs (all P < 0.05). Among HPIV-1-positive children, respiratory and non-respiratory complications occurred in approximately one-third and two-fifths of cases, respectively, with over 95% achieving clinical improvement or discharge. Patients with severe pneumonia, compared to non-severe cases, demonstrated significantly elevated inflammatory markers, prolonged fever, higher rates of complications and ICU admission, increased respiratory support requirements, longer hospital stays, and higher costs (all P < 0.05). HPIV-1-positive pediatric ARI patients have a high co-detection rate, with HPIV-1-virus-bacteria co-detection being the predominant pattern. Co-detection is linked to greater disease severity compared to mono-detection. Key indicators for severe pneumonia include elevated inflammatory markers, prolonged fever, complications, and respiratory support needs. IMPORTANCE Human parainfluenza virus type 1 (HPIV-1) is an underrecognized contributor to pediatric acute respiratory infections (ARI), yet its clinical impact remains unclear, particularly regarding co-detection with other microbes. Based on targeted next-generation sequencing (tNGS), this study demonstrates that HPIV-1 detection in hospitalized children with ARI is characterized by a high rate of microbial co-detection, which is associated with greater disease severity. Elevated inflammatory markers (procalcitonin [PCT] and erythrocyte sedimentation rate [ESR]), prolonged fever, complication occurrence, and need for respiratory support serve as key predictors of progression to severe pneumonia in these children. These findings offer important clinical evidence to support the development of a predictive model for severe pneumonia in HPIV-1-positive children and provide valuable guidance for optimizing diagnostic and therapeutic strategies for HPIV-1-associated respiratory infections.