I'm writing a story, in which the detective will recognize a prescription for the victim is for relief of some genetic condition.
You wanted to be realistic: In the autopsy report (after any murder, they usually cut the corpse open and search for clues - and for causes of death), the genetic condition would have usually shown.
Humans are the only known animal that the disease affects naturally. However, chickenpox has been caused in other primates, including chimpanzees and gorillas.
The varicella zoster virus cannot infect dogs.