Re: Question... Evolution at work?

On Thu, 24 Nov 2005 10:25:33 -0500, "Robert J. Kolker"
<nowhere@xxxxxxxxxxx> wrote:

>Cyde Weys wrote:
>
>> immune or had fought it off successfully, thus gaining antibodies.
>> 2. Its morbidity outmatched its virulence. This is the problem ebola
>> has - it's too damn deadly to actually spread very fast.
>
>Correct. Only the weakest pathogens survive because the strongest have
>killed off their human reservoirs. This is a case were weak is fit and
>strong is not.

Parasites that kill their hosts are at a distinct disadvantage only
when jumping to a new host is difficult. Under those circumstances,
killing the host is usually an indication that the host is fairly new.
The "natural" host is probably not harmed that badly. However when
the parasite is very easily spread even from dead hosts there is no
advantage in being "gentle". Defining weak vs. strong simply in terms
of virulence or morbidity is just an inappropriate way of looking at
things. Epidemiology has pretty good mathematical models that predict
both the rapid spread and abrupt termination of disease outbreaks
based on population density, percentage of susceptible individuals,
rate of contagion or spread, etc.

>> 3. Public health warnings succeeded. There is good indication in the
>> case of the 1918 flu that the advice to frequently wash hands and in
>> all ways stay very clean helped to limit its spread.
>
>
>> 4. Effective quarantine of infected individuals.
>
>Hygiene and good habits are at least as effective as anti-biotics.
>

The major increases in longevity and general health in the western
world came about before the era of antibiotics, when the recognition
of bacterial origin of disease produced public health measures in
water supply, sewage disposal, and food distribution. Those still are
major barriers to health in many parts of the world. There are most
definitely diseases where simple public health measures are not
appropriate but most westerners now die from "degenerative" changes in
physiology and cell biology like heart disease and cancer rather than
infectious disease. That could dramatically change, though, without
constant vigilance.




.

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