Vassiliki et al. also found virus infection was negatively associated with the number of CD4+ (P = 0.030), CD8+ cells (P = 0.030), CD4+CD45RO+ cells (P = 0.030), and CD8+CD45RO+cells (P = 0.050) after umbilical cord blood transplantation [28]. This evidence concerns the gene CD8A and viral infectious disease.