I was taught that viruses are weird little machines, similar but unrelated to the things we recognise as alive. Interesting that there's difference of opinion on the matter.
Edit: here's a question for the room; if viruses are unrelated to the rest of "life", but are endogenous to the earth, are they alien?
Edit: here's a question for the room; if viruses are unrelated to the rest of "life", but are endogenous to the earth, are they alien?