Re: diseases and immunity

Fred G. Athearn (
14 Jul 1996 06:47:16 -0400

>>>>> "Gerold" == Gerold Firl <> writes:

Mary Beth> Gerold, you're taking a cite from a cite as
Mary Beth> hard evidence, and you're not even sure of the
Mary Beth> primary data from which the interpretation
Mary Beth> derives? Not very scientific, wouldn't you
Mary Beth> say?

Gerold> Oh, I don't know. I'm giving you what data I have. Is
Gerold> it "hard evidence"? I consider mcneill to be pretty
Gerold> reliable, and it is certainly a well known fact that
Gerold> unfamiliar diseases will manifest unusual symptoms
Gerold> and virulence....

If we assume for the sake of argument that TB had the
spectacular sort of virulence you suggest in early Indian
populations there remains the problem of transmission. How is a
disease that kill within weeks transmitted? Clearly not in the
way TB seems to be today.

Mary Beth> The most plausible present-day hypothesis is
Mary Beth> that Old World *yaws* and New World endemic
Mary Beth> syphilis interacted and formed a new more
Mary Beth> lethal strain of the organism.

Gerold> ...bacteria constantly exchange dna, so advantageous
Gerold> genes spread very quickly in a bacterial population.

If syphilis (as Gerold suggests) killed within days of exposure
when it first came to the old world that would have place very
big limits on its ability to propagate itself as a sexually
transmitted disease.

In that context genes from a local endemic disease which slowed
down the progress of the infection by marking it for immune
system attack could be considered "advantageous".

Gerold> ...In an unexperienced host population,
Gerold> however, the virulent strains will be the most
Gerold> successful. They will rapidly and aggressively expand
Gerold> their market-share, until the epidemic burns out and
Gerold> the chronic strains take over.

It is incorrect to jump from the idea of virulents to the idea of
raging and expanding epidemic.

The fact remains that any theory of a blitz krieg attack on the
American Indian population by one very virulent disease needs to
explain how transmission could take place between groups that
were quite spread out.

This is not just a problem of history. There is an arithmetic to
epidemics that has to be taken into account. It seems that to
make your theory work you would need to come up with a different
transmission method for TB within the target population.--
Fred G. Athearn
Rockingham, VT, USA finger for pgp key (802) 869-2003