CD34 and disease arising from reactivation of latent virus: Human cytomegalovirus (HCMV) remains a significant cause of morbidity and mortality after solid organ transplant and hematopoietic stem cell transplant (1, 2) due to the ability of the virus to establish a latent infection in CD34+ hematopoietic progenitor cells (HPCs) (3, –, 5).