Clinical Associations and Coexistence of Polyomavirus DNAemia with EBV and CMV in Pediatric Hematology/Oncology Patients, Including HCT Recipients—A Pilot Study

Polyomaviruses (BKPyV and JCPyV) and herpesviruses (EBV, CMV) usually infect people during childhood, and may be associated, in some clinical states, with immunocompromised individuals. The aim of this study was to investigate the occurrence and coexistence of polyomavirus (BKPyV and JCPyV) and herpesvirus (CMV and EBV) DNAemia in pediatric hematology/oncology patients, including HCT recipients, and to assess the clinical relevance of polyomaviruses DNAemia. Whole blood samples of 99 children (including 71 patients undergoing HCT) were analyzed for the DNA of the herpes- and polyomaviruses. Co-existence of herpesvirus DNAemia was checked for the patients and clinically analyzed in detail, especially for those positive for BKPyV DNA. BKPyV DNAemia was detected in 15 (15.2%) patients, with viral loads ranging from 1.2 × 10³-1.7 × 10⁷ DNA IU/mL. No JCPyV DNA was detected in any of the samples. Coinfections with EBV or CMV DNAemia were observed in a subset of BKPyV-positive patients. BKPyV DNAemia was more frequent among children with leukemia and in those undergoing HCT. Our findings highlight the clinical associations between BKPyV and herpesvirus DNAemia in immunocompromised pediatric patients. Routine BKPyV DNA monitoring, alongside standard herpesvirus screening, may provide clinically valuable insights in high-risk pediatric cohorts, particularly those with hematologic malignancies and post-HCT status.