Severe Lower Respiratory Tract Infection in Patients With Human Bocavirus Monoinfection in Southeast China.

Abstract

This study aims to investigate the severity and risk factors of acute lower respiratory tract infections (LRTIs) caused by human bocavirus (HBoV) in children. We conducted a prospective cohort study of children hospitalized with LRTIs and confirmed HBoV monoinfection via polymerase chain reaction from March 2022 to February 2024. Viral load and genome analysis were performed, with clinical data collected. Patients were followed for 1 year post-discharge. Among 412 hospitalized patients with HBoV-positive LRTIs, 268 (65.0%) had HBoV monoinfection. Severe infection occurred in 45.5%, with 10.8% critical, 6.3% requiring ICU admission, and 2 (0.7%) deaths. Higher HBoV-DNA loads (>10⁶ copies/mL) significantly increased critical disease risk (OR1 = 9.33, 95% CI 2.90-30.09). IFN-γ levels weakly correlated positively with DNA loads (r = 0.20, P = .024) and neutrophil counts (r = 0.26, P = .003). Furthermore, elevated neutrophil counts (>60%) were associated with hypoxemia (P < .001), pulmonary consolidation (P = .034), critical LRTI (P < .001), and ICU admission (P < .001). Despite high HBoV conservation, the VP1_40 (L→S) amino acid variation significantly increased critical LRTI risk (P = .03). HBoV monoinfection can cause critical LRTI in children. High DNA load, associated with elevated IFN-γ levels and neutrophilia, along with the viral VP1_L40S variant, may be key factors contributing to severe disease outcomes.