Where do viruses come from?

We put this question to Cambridge University Researcher Ed Hutchinson...

In the case of flu, you've got the fact that flu will spread from organism to organism so although we're worried particularly about a human virus, or a virus of livestock as well, it actually starts off as a virus in waterfowl. Things like ducks, where it's not really a pathogen at all - it just lives in there and gets along with them. That doesn't really tell you where a virus has come from. We know that they can spread from organism to organism.

In the first place viruses probably evolve as just bits of the genetic sequence which just get out of hand and start copying themselves, moving to places they shouldn't and acquiring more and more abilities along the way. There are quite a few examples of this where thing start jumping around inside genomes eventually will get the ability to jump from cell to cell as well.

Chris - In the answer to what came first, chicken or the egg, the virus-cell situation has to be the cell came first, the virus came later?

Ed - Remember, the defining feature of the virus is that it's absolutely dependent on taking over a cell to work. Without a cell the virus isn't going to do anything at all...