Some bacteriophages inject their genomes into bacterial cells (to not scale) Viral populations don't increase by way of cell division, because they are acellular. Shingles only occurs in people that’ve had chickenpox sooner or later. It’s a reactivation from the varicella-zoster virus that’s been lying dormant with your cells. https://www.youtube.com/watch?v=Lkhoy9awOCU