Was it you? Because we were dealing, with among other issues, the HPV/ cancer link. (The ‘H’ in HPV is for ‘Human’). But in the end, ‘animals is animals’. And a number of cancers have a viral origin.
I think the difference is that, in these cases, the cancer itself is what is transmitted. There’s another one (in dogs or cats, I can’t remember) that is sexually transmitted, and is the same way - kills ‘em all once they’ve got it. Human viruses such as HPV get transmitted all the time, but relatively few become cancerous, and even then most are fairly treatable.
I ain’t no microbiologist, though, so take it for what you will.