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From: Henry Spencer <>
Subject: Re: Mars outpost, crew considerations
Date: Tue, 12 Aug 1997 22:19:57 GMT

In article <>,
Maggie Pereyra  <> wrote:
>> Does anybody know how to predict which way it goes?  When the
>> Spanish Conquistadors came to Mexico, many native Americans died
>> from the diseases brought from Europe because their immune systems
>> were not ready to deal with the new bugs.  But why were the
>> Spaniards not equally affected by American bugs that their immune
>> systems were not ready for?
>What about syphilis?

There is some evidence that syphilis may have come from the Americas (and
in early days in Europe, syphilis was a rapid and devastating disease --
the much milder form seen in recent times is presumably a mutated strain
which has survived better because it's easier on its host).  There are a
few other significant diseases which are definitely of Western Hemisphere
origin, but in general they haven't succeeded in establishing themselves

In general, though, one would expect things to mostly go the other way,
because the two populations were very different.

Eurasians had been living in large cities for thousands of years,
incubating diseases in the process.  They also lived with and exchanged
diseases with a number of types of domestic animals.

The folks who crossed the Bering Strait into the New World were few in
number, and the long and harsh journey ensured that most of them were
healthy and that the Old World diseases were mostly left behind.  Contact
with more settled parts of the world was minimal for thousands of years
thereafter, and again it tended to involve small numbers and long harsh
journeys.  In places the Amerinds did eventually build cities, but they
were small and recent by comparison with those in Europe and Asia.  And
there were few domesticated animals in the New World, probably because
most of the large New World animals were extinct before domestication was
ever considered.
Committees do harm merely by existing.             |       Henry Spencer
                           -- Freeman Dyson        |

From: B. Harris)
Subject: Re: chlamydia test
Date: 3 Jun 1998 08:47:38 GMT

In <> nicole <> writes:

>	One difference between the two scenarios is that in the case of
>chlamydia contacts in contemporary society, there are sensitive tests
>available.  For soldiers in the jungle, this was not a viable option.
>As a result, the case for presumptive treatment of the soldiers would be
>stronger rather than weaker.  The fact that they had multiple contacts
>and that these contacts (prostitutes) were not treated (resulting in
>ongoing exposure) also weighs in favor of presumptive treatment.
>Although the complications of untreated chlamydia infections can be
>serious, the complications of untreated syphillis can be even more
>devastating.  Again, the difference seems to make the case for
>presumptive treatment in Nam more rational rather than less.

    You're switching diseases on me.  Syphilis is not the same disease
as chlamydia, and with all diseases, risks and benefits have to be
looked at when you decide to treat presumptively.  Syphilis hasn't
become resistant to penicillins to this day, and its inability to
acquire such resistance was known in the Vietnam era, and the reason
for it also (it doesn't have "sex" with other bacteria, for one thing).
Treating soldiers prophylactically for syphilis made as much sense as
treating them prophylactically for malaria, and for the same reasons.
I'm not talking about that.  It was a good idea, and in fact it did
work.  The same reasoning, however, did not apply to treating them in
the same way for gonorrhea or clamydia, both practices which resulted
in rapid antibiotic resistance without doing a lot of good for the
soldiers (not too many lives saved).

>The population of people exposed to partners with chlamydia (around 16
>million) is also far greater than the number of soldiers presumptively
>treated in Nam. If you took the presumptive treatment recommendation to
>its logical conclusion, the implications with respect to resistence would
>be enormous. I am not refering to prospect of resistent chlamydia, but
>the effect on the community flora generally (as a physician I am sure you
>appreciate the mechanics of gene transfer among bacteria).

   Yeah, I do.  Do you?  I've not especially worried about general
resistance to the kinds of antibiotics used to treat chlamydia, which
are the macrolydes and tetracyclines.  We've pretty much played them
out with the more serious infections anyway, and resistance to these
among gut organisms is widespread anyhow.  Again, you need to look at
costs vs benefits.

                                         Steve Harris, M.D.

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