Malcolm  wrote:

> "Tim Tyler"  wrote in message
> >
> > The fate of most such viral infections is to make peace with their hosts -
> > and to become less life-threatening.  This is what has happened to
> > the equivalent of HIV in our cousins - for example.
> >
> This is a bit of a fallacy, that parasites eventually evolve to mutually
> beneficial relationships with their hosts. All the virus cares about is
> getting out of that host and into a new one so it can complete its
> lifecycle. If this is achieved by making the host live longer then mutualism
> will evolve. However if the virus multiplies massively are tries to flood
> the environment with copies, then probably the host will be killed in the
> process.

There's a good and extended discussion of the Burnet-Medawar Hypothesis
in Ewald's book. In summary, he thinks that the only time mutual
symbiosis evolves is when the genetic fitness of the parasite/pathogen
is linked closely to that of the host's - i.e., when it is hard to
spread the disease. If the vectors are such that fitness of the pathogen
and fitness of the hosts and vectors are not linked, they can be
expected to become *more* virulent, not less. So the best thing to do
with something like AIDS/HIV is, reduce the frequency of transmission.
Condoms and limited sexual contact are obvious tools here.

Ewald, P. W. (1994). Evolution of infectious disease. Oxford [England];
New York, Oxford University Press.
        
-- 
John Wilkins
DARK IN HERE, ISN'T IT?
wilkins.id.au
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 12/10/03 6:23:08 AM