CD34 and disease arising from reactivation of latent virus: Supporting this assertion, deletion of the US27, UL33, and UL78 genes does not affect the establishment of HCMV latency, whereas deletion of the US28 gene has profound effects on latent infection in CD34+ progenitor cells and leads to lytic infection in these undifferentiated myeloid cells, due to a lack of MIEP repression (21).