You can kill it in the sense that you stop it being a mutating replicator. That is pretty much the bare bones of life, an abstraction you can't get away from in defining life, but also one that encompasses things that aren't "life". It also applies to things like memes (both the original form from Dawkins and the internet form).
A virus is not a replicator. It is information and a transport system. The machinery of a living cell is the replicator.
It seems pretty simple to me: viruses are not living. They are able to co-opt living systems into making more of themselves.
A virus may gain life while it is inside of a cell, but why is that any different than the organic molecules which gain life when assembled into a cell? We don't say carbon is alive.
For something to be a replicator, what does that mean? Surely just that it somehow causes more of itself to be made, and has enough variability to change its descendants. A particular organic molecule like say a simple sugar doesn't fit this, because its structure is always the same. But a DNA strand can actually be any of many similar structures.
I think the distinction between what is doing the replication is spurious. The fact is even living replicators need some sort of base resource to exploit to pull off the feat. I could say that animals aren't replicators, because they inherently require other living creatures to be eaten in order to replicate.
To me, for some thing to be a replicator, that thing must include the machinery for replication. Viruses do not include that machinery. Cellular life does not include the food required to replicate, but it has the information, the machinery, and the mechanisms to gather the required resources. It is, I think, somewhat arbitrary where you draw the distinction, but it seems useful to divide replicators which do not include machinery from those that do. There are probably things which sit on this divide and make it hard to draw a distinction. That's life. It's not required to fit into our mental and linguistic bins I suppose.
So they're a parasite. There are insects that can only reproduce by laying eggs inside of another insect. They don't physically carry their own. Does that mean they're not alive?
