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Originally Posted by punky
We shouldn't get too excited. This is one scientists opinion, and as the article said, another has contradicted it.
I'd be very suprised if the virus is weakening, as it certainly bucks the trend. Viruses evolve like all other life forms, and they evolve to become stronger, more suited to the environment, and more resistant to drugs (i.e. become a new strain so old drugs no longer work).
But who knows?
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As a matter of fact, organisms don't evolve to become stronger, they evolve to survive: survival to breed is the driving force of evolution.
New viruses are frequently extremely virulent because they are poorly adapted to their host's body: this is actually contra survival for them. They need to reproduce, and they need the living cells of their host's body to accomplish this in. An extremely virulent virus may even kill its host before it can effectively reproduce - that strain will, clearly, rapidly become extinct!
As new viruses that do survive move into later generations, the strains that don't kill their hosts as readily survive better, since they have more time and resources to reproduce. Over time, this means that the evolutionary tendency of a virus is to become less virulent, and the less virulent it becomes, the more successful it is.
Over time, it evolves to where it no longer kills its host, and then further to become parasitic rather than pathogenic: i.e. it not only does not kill its host, it doesn't even do it excessive harm. Eventually, it may even become part of the organism it infects.
The reason why this is is advantageous is that evolution is not about survival of the organism: this is a vehicle. It's about survival of the genes. And when a parasitic organism finally becomes absorbed into its host, its genes become part of the host's genes and survive, presumably even more successfully, because of that.
Our genes, in fact are, in some part, made up those of the organisms that have infected our ancestors in the past. Even parts of our cells, like the mitochondria, are derived from other organisms such as primitive bacteria.
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