>The only problem (as I know you know -- no professor hat on here) is that viruses constantly mutate. They stay one step ahead of the law, so to speak. It's fascinating how these brainless organisms manage to alter themselves enough to avoid extinction. Every year the flu is back, but it's a slightly different flu from last year's. My hat is off to those with the brainpower to really dig into it.

It's survival of the fittest. The mutations that make the virus more able to survive win out over those that don't. In fact, I've read that that's one reason so few bugs actually kill us; killing the host doesn't lead to long-term survival for a virus or bacterium.

Tamar