The ribosome is the central effector of protein synthesis, and its synthesis is intimately coordinated with that of proteins. At present, the most documented way to modulate ribosome biogenesis involves control of rDNA transcription by RNA polymerase I (RNA Pol I). Here we show that after infection of human cells with herpes simplex virus type 1 (HSV-1) the rate of ribosome biogenesis is modulated independently of RNA Pol I activity by a dramatic change in the rRNA maturation pathway. This process permits control of the ribosome biogenesis rate, giving the possibility of escaping ribosomal stress and eventually allowing assembly of specialized kinds of ribosomes.