165 - Adolescent Viral Lower Respiratory Tract Infection: Pathogen Shifts and Sepsis-Linked Severity Patterns in a Five-Year Cohort

Publication Number: 1155.165

Jacob Z. Hesen, Hurley Medical Center, Undergraduate student, University of Michigan, Flint, MI, United States; Mahesh Sharman, Michigan State University College of Human Medicine, Flint, MI, United States

Background: Most pediatric lower respiratory tract infection (LRTI) research has focused on young children, leaving limited understanding of age-specific differences in viral etiology, immune response, and clinical severity during adolescence.

Objective: To characterize age-specific pathogen distributions, physiological and clinical outcomes among adolescents, compared with younger children presenting with viral LRTI.

Design/Methods: A Retrospective cohort study of PCR-confirmed viral LRTI from January 2019-December 2024, using ICD-10 codes. Patients were grouped as adolescents (≥ 12 years) or < 12.

Primary outcome: Pediatric Intensive Care Unit (PICU) admission.
Secondary outcomes: respiratory support level, antibiotic therapy, and changes in sepsis-related parameters: Heart rate (HR), corrected HR, Respiratory rate (RR), corrected RR, blood pressure, cardiorespiratory instability index (CRII), C-reactive protein and white blood cell count (WBC).
Analyses included nonparametric and logistic regression models (robust SEs, penalized/Firth fallback), with false-discovery-rate (FDR) correction. The study was IRB approved with waiver of consent.

Results: Adolescents comprised 12.6% (1523/11,926) of the cohort and had lower positivity for Respiratory Syncytial Virus [RSV] (2.4% vs 16.1%), and Rhinovirus/Enterorvirus [RV/EV] (23.6% vs 42.0%), all q < 10⁻²³, but higher prevalence of Mycoplasma pneumoniae (4.9% vs 1.6%, q < 10⁻¹⁶) with less confection. [Table 1]
Despite reduced viral burden, adolescents exhibited greater need for invasive mechanical-ventilation [MV] (3.3% vs 1.2%, q < 10⁻⁹) , pediatric intensive care admission [PICU] and higher antibiotic exposure (37.7% vs 27.6%, q < 10⁻¹⁵). Among adolescents, the proportion with CRII ≥2 was 24.0% vs 15.3% in younger children (risk difference 8.8%, 95% CI 5.9-11.6%; RR 1.57; FDR-adjusted p < 1×10⁻¹¹ (Figure 1 ). Median CRP was 29.9 mg/L in adolescents vs 9.9 mg/L in younger children (q < 10⁻²³). Adjusted models confirmed an independent association between adolescent age and MV (aOR ≈ 2.5, 95% CI 1.7-3.7) and antibiotic use (aOR ≈ 1.6, 95% CI 1.3-2.0), but not oxygen therapy or CPAP/BPAP.
An inverse association of adolescent age with RSV (aOR ≈ 0.09) and RV/EV (aOR ≈ 0.42), and a positive association with Mycoplasma pneumoniae (aOR ≈ 3.2) was noted.

Conclusion(s): Adolescents with viral LRTI exhibit distinct pathogen and host patterns. Despite lower viral detection, adolescents have greater physiologic instability and higher needs for MV and antibiotics. These results suggest that host factors, not pathogen burden, drive the increased severity seen in this age group.

Table 1. Demographics and Clinical Characteristics of adolescents compared to younger children
RV/EV = Rhinovirus/Enterovirus, PICU= Pediatric intensive care unit.

Figure 1. Predictors of Pediatric Intensive Care Unit (PICU) admission.
x-axis: adjusted Odds ratios for PICU admission (log scale). vertical dashed line: the line of no effect. Blue and red marks highlight physiologic severity scores (Cardiorespiratory Instability Index [CRII] and quick Sequential Orang Failure [qSOFA]). Black marks: demographics and clinical variables.