Feline Leukemia Virus, despite the name, is NOT a cancer- but a retrovirus. It spreads cat-to-cat by saliva, shared bowls, feces and urine, etc. Humans and dogs can NOT get this and the virus does not survive well outside of the feline host- so it is manageable

While their lifespans are shortened, FeLV cats can live decently long, happy lives and many survive 3-5 years after diagnosis. This virus affects the immune system, so while FeLV is generally not painful in itself- it can cause many complications