Are humans a virus on earth?

Well, if you are right, then there is no such thing as ethics or morality and so there is nothing wrong with a "virus" fulfilling what evolution has brought us to do. I'm all for 'infecting' the universe and fulfilling our destiny. People seem to like the claim that humans are just like any other animal on the evolutionary ladder; just like your hypothetical virus. Yet they imply that we should be ethical and "control" our primal instincts. A virus' purpose is not to kill it's host... it is to reproduce... and the only way a virus can reproduce is by using a pre-existing cell. They do not reproduce by mitosis. If you want to look at it from a strictly biological point of view, humans and any other multicellular organism are about as different from a virus as you can get. In fact there is quite a bit of argument as to whether we should clify virus' as life at all. It's harder than you think to kill a planet.