ZAP70 and B-cell chronic lymphocytic leukemia: Higher EBV DNA-copy number (>1000 copies/μg of DNA) in PBMCs of patients at CLL diagnosis was significantly associated with other established unfavorable prognostic factors, such as the IGHV mutational status, CD38-positive or ZAP-70-positive phenotype of CLL cells, and the presence of the del(11q22.3) cytogenetic abnormality [28,29].