purpose of viruses??

Giovanni Maga maga at vetbio.unizh.ch
Wed Feb 1 08:45:50 EST 1995


In article <rrg.1018.000CB9E9 at aber.ac.uk>, rrg at aber.ac.uk (Roy Goodacre)
wrote:

> In article <anh-2401950740200001 at mac-burl-11.dfci.harvard.edu> anh at macmailgw.dfci.harvard.edu (Anh Nguyen) writes:
> 
> >I agree with you Mark. I would argue that the "purpose" of viruses, as
> >with all living organisms,is to propagate their genetic material. Viruses
> >are just a little more aggressive in their pursuit of this goal.
> 
> Yes another agrees.  The aggressiveness can be really very high, Ebola Zaire 
> for example kills 9 out of 10 human hosts in <14 days.  I'd speculated that, 
> for the virus, this is not too good an idea as if you want to spread your 
> genetic material if your are too pathogenic then you eventually loose your 
> host. 
> Roy
> 
>
I agree Roy. I think we can consider viruses as parasites and so their
strategies should be similar: the perfect parasite is the one who does not
kill its host until its life cycle is complete and the host itself can
reproduce. Thus, the host/virus relationship usually evolves until the
mortality caused by the virus is not enough to decrease significantly the
population of living hosts. A special case could be the one in which death
of the host is necessary for the spreading of the parasite, but also in
such a case there must be an equilibrium between the loss of hosts and the
number of parasites. Otherwise it should be cosidered an intermediate step
in the adaptation process. Very aggressive viruses I think should be
considered as newly aquired parasites not yet adapted to their hosts.
G. Maga



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