Good question. Thank you. (A nice break from what I had planned to do.
) What came to my mind is a quote, "Viruses today spread genes among bacteria and humans and other cells, as they always have... We are our viruses
" by Lynn Margulis, 1998, Symbiotic Planet: A New Look at Evolution, Basic Books, 1998. p 64. This link tells you about Lynn Margulis. If you would like more information about her I can provide it.
And what a fasinating and awe inspiring world it tiss even when one is flat out tired from a four day wedding event of a good friend.