Epidemiology and Clinical Spectrum of Human Bocavirus Infection in Children: A Retrospective Single Center Analysis

Background: Human bocavirus is a non-enveloped DNA virus of the Parvoviridae family, first identified in 2005 and is recognized as a respiratory pathogen across pediatric age groups, with the highest prevalence reported in children aged 6–24 months. Interpretation of HBoV infection is complicated by frequent viral co-detection and the lack of a reliable method to distinguish active infection from prolonged viral sheding. Methods: We analyzed epidemiological trends and viral co-detection rates, along with demographic, clinical, laboratory, and radiological features of patients aged 0–18 years infected with HBoV during a four-year period (2022–2025) at a tertiary pediatric center in Croatia. Results: Of 27,361 respiratory samples collected, 1143 (4.2%) were positive for HBoV. Annual detection rates remained stable (3.6–4.8%), with predominant winter circulation. Viral co-detection was frequent (71.0–82.7%), with adenovirus and rhinovirus being the most commonly co-detected viruses. Pneumonia was diagnosed in 23.7% of patients, with age > 24 months (aOR 2.32; p = 0.012) and higher leukocyte count (aOR 1.13; p < 0.001) recognized as associated factors. Severe disease was uncommon: seven patients required oxygen support, and four were admitted to the PICU. Around one-quarter had gastrointestinal manifestations. Prolonged HBoV detection was observed, with the longest interval being 291 days. Conclusions: This is the largest single-center study of HBoV infection in the general pediatric population in Croatia. HBoV was predominantly detected in toddlers, with frequent viral co-detection, although HBoV-related pneumonia was more common in older children. Further studies are needed to clarify the role of HBoV in respiratory illness.