Re: diseases and immunity

Mary Beth Williams (
16 Jul 1996 12:20:23 GMT

In <4sebpn$> (Gerold Firl)
>In article <>, Fred G. Athearn
<> writes:
>|> >>>>> "Gerold" == Gerold Firl <> writes:
>|> 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.
>I'm not sure how TB is transmitted, though I've always assumed that it
>was by inhalation of the bacilli within a drop of sputum (ever heard
>someone with TB cough? Nasty.)
>Here's a simple model of the population dynamics of a pathogen upon
>reaching a virgin-soil host population: instead of taking several
>years to die, these new hosts die in several days or weeks. They are
>also totally open to infection, with no appreciable immune reaction.
>This results in a new selection pressure on the pathogen: it needs to
>jump to a new host quickly, and it doesn't need to be very picky about
>what part of the body is colonized.
>The pathogen thus evolves to become highly contagious, which, in
>practical terms, means being able to survive temperature fluctuations
>and dessication. Using TB as an example, it also will change so-as to
>no longer restrict itself to the lungs. (Bacteria have a varied
>repertoir of cell-membrane proteins which attach to different host
>tissues; lungs, intestines, blood cells, nerves, cartilage, etc) In an
>immunilogically experienced population, TB resides in the lungs; in an
>inexperienced host, that restriction is no longer necessary.

Wrong, wrong, wrong... Haven't you read _anything_ I've posted? TB
does _not_ reside only in the lungs in *immunilogically experienced*
populations! If this were so, then we'd have NO evidence of TB from
Europe and Asia, as the ONLY evidence in any dead populations is
skeletal, i.e., you can't tell if someone died from pulmonary TB.
Skeletal TB effects 3-5% of ALL cases of TB, not only in *virgin soil*

>As soon as TB invaded amerindian populations, the new environment led
>to an evolutionary shift. Highly contagious strains were favored,
>since the less-contagious ones died along with their hosts, while more
>transmittable strains had already infected a few other people before
>their host died.

Geez, Gerold, where do you come up with this crap? TB remained *highly
contagious* in all densely congregated populations, Indian or white,
until the 20th century. Go back and read some vital statistics records
from New England in the 19th century, and you'll find that
*consumption* accounted for nearly 50% of all *natural* deaths between
the ages of 18-50, and *lung fever* (rapid pulmonary TB) ranked up with
yellow fever, measles and smallpox.

>A big factor there is the way people will flee from an epidemic.
>Crosby describes how refugees from disease spread it far and wide,
>probably accounting for the devastation of the mound builders, far
>ahead of any colonization.

AH HA HA HA!!!!!! So Europeans were running around North America in
the 13th and 14th centuries???? The *moundbuilder* (early
Mississipian) cultures, particularly those in the American Bottom
region, e.g., Cahokia, dispersed prior to 1400. And there is no
evidence that they *died* out, rather that they emigrated to the
Southeast, and/or moved into smaller settlements away from the big
rivers and heirarchical societies.

MB Williams
Dept. of Anthro., UMass-Amherst