Risk Factors for the Development of Bronchiolitis Obliterans Following Adenovirus Infection in Children and Its Association with the COVID-19 Pandemic: Five Years of Data from a Single Center

Objective: Post-infectious bronchiolitis obliterans (PIBO) is a common form of bronchiolitis obliterans in children. It can arise from various respiratory tract infections, including adenovirus. This study aimed to identify risk factors for the development of PIBO in pediatric patients following confirmed adenovirus infection. In addition, to review if the COVID-19 pandemic altered the frequency this occurred. Methods: This retrospective study included 516 pediatric patients (age 0-17 years) with confirmed adenovirus infection, who subsequently developed PIBO. For each patient demographic data, clinical characteristics (including oxygen supplementation, mechanical ventilation, ICU admission, duration of hospitalization), laboratory parameters (complete blood count, erythrocyte sedimentation rate, C-reactive protein), imaging findings (chest radiography, computed tomography), viral co-infections and patient comorbidities were collected. Patients who developed PIBO were compared to those who did not. Results: The median patient age was 48 months (range: 1-216 months) and 58.7% were male. Adenovirus infections were most prevalent in winter (n=218, 42.2%), followed by spring (n = 138, 26.7%). PIBO was diagnosed in 20 patients (3.9%). Those who developed PIBO required significantly more oxygen supplementation, had longer hospitalizations and higher rates of ICU admission whilst infected with adenovirus. In addition, those with PIBO had more comorbidities, specifically immunodeficiency (primary or secondary) and acute lymphoblastic leukemia (all p < 0.05). The COVID-19 pandemic did not significantly alter the frequency that PIBO occurred following adenovirus infection. Conclusion: Primary and secondary immunodeficiency emerged as a potential risk factor for developing PIBO following pediatric adenoviral infection. Our findings underscore the potential value of immunologic screening in patients diagnosed with PIBO without any other clear risk factors.