

MIT researchers solve mystery of the 1918 "Spanish Flu" pandemic - pmikal
http://www.dailygalaxy.com/my_weblog/2009/07/solving-the-mystery-of-the-1918-spanish-flu-pandemic.html

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steve19
Isn't a flu virus like spanish flu an evolutionary mistake? Killing your host
is a bad way to passed on. The penalty for the "mistake" is that the strain,
or at least its notable features, no longer exist.

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dflock
It depends on how quickly you kill them and how you do it. Cholera victims go
out in a flood of infectious watery diarrhea, thus spreading the virus to
people in the vicinity and into the ground water, passing the infection along.
Ebola does something horribly similar, except with blood and liquefied
internal organs. The diarrhea you get with cholera is mostly your body trying
to flush out the bacteria and toxins from your gut. Cholera has evolved to
exploit and exacerbate this defense mechanism to spread itself. Sneezing is
that same principle, for respiratory infections. These dramatic death throws
can be viewed as a very aggressive means of the infection passing itself
along, after having completely exhausted the capacity of the current host to
produce more virus or bacteria. Even though these are both extremely lethal
and fast acting diseases, they're both successful, evolutionarily speaking.

If there was a flu strain that made you sneeze so much that you eventually
died from it (dehydration, hemorrhage?), this would be similar. As it is, it's
generally your immune system going nuclear, an opportunistic infection,
underlying poor health or a combination that kills you with influenza.

Quite a lot of the pandemic potential of diseases depends on us and the
opportunities we give them. Ebola has thus far proved too lethal and too quick
to spread very widely - and because it's a terrifying disease, we've cracked
down on it very hard. Cholera - which is actually more lethal and even faster
acting than Ebola - was the scourge of the 19th century, killing tens of
millions of people, before we figured out about pubic health and sanitation,
taking away it's opportunities.

So, no. Killing people isn't an evolutionary mistake for an infectious
organism. It's an evolutionary adaptation - a way of pumping out as many new
bacteria or viruses into the environment as fast as possible and then moving
on, before the hosts immune system catches up with you. If you take it easy
and go for the slow burn, generally the hosts immune system will wipe you out.
If you want to do that, then you need a different evolutionary adaptation to
evade the immune system for long periods, like HIV does.

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fauigerzigerk
But the common cold is slow, non-lethal and still ubiquitous. It seems unclear
to me what success really means in this context.

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anamax
Success means "not extinct".

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fauigerzigerk
Yes but among those who survive, is the common cold virus more successful than
ebola? I don't think there's a good answer to that.

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anamax
That's because "more successful" is not a good question.

Unless one or the other dies out, they're both successful and that's all that
you can really say.

The common cold is more common than Ebola. That may help the common cold
survive longer. If it does, and we suspect that it does, then "common" was
useful. If, on the other hand, that "commonality" makes us so mad that we go
all out to kill it and succeed (like we probably have with small pox and might
soon with polio), "common" worked against it.

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fauigerzigerk
I agree with what you say, but I was trying make an entirely different point,
which is that I don't think success is the right word to describe anything
related to evolution.

Success implies goals and evolution has no goals. A particular species
surviving or not is just like rolling a die and observing that the 3 has come
up and the other numbers didn't. It's useless to say that 4 wasn't successful.
Nobody would say that, but when it comes to evolution people start to talk
about success as if nature had intentions.

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anamax
> Success implies goals and evolution has no goals.

I agree, but evolution does have results. The one that drives everything is
survives.

