Newsgroup: it.discussioni.misteri
Titolo: [Aral] le spore di Anthrax muoiono difficilmente

http://www.tigerherbs.com/eclectica/earthcrash/news/1999/06/02-5.html
(...)
Military scientists at the U.S. Army Medical Research and Material
Command and other laboratories where the samples are being studied
refused comment on the island and the tests. But other officials said
the labs were still deciphering the Russian anthrax's molecular
structure and trying to determine why spores collected from some of
the pits did not die. "We have always known that anthrax is hard to
kill," said one military expert, who would only discuss this highly
classified activity if he were not identified. "But this strain has
proven especially durable, and this wasn't even the most powerful
strains the Soviets made."
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Background and Epidemiology
Anthrax is one of the great infectious diseases of antiquity.
The fifth and sixth plagues in the Bible's book of Exodus
may have been outbreaks of anthrax in cattle and humans,
respectively. The "Black Bane," a disease that swept through
Europe in the 1600s causing large numbers of human and animal
deaths, was likely anthrax. In 1876, anthrax became the first
disease to fulfill Koch's postulates (i.e., the first disease
for which a microbial etiology was firmly established), and 5
years later, in 1881, the first bacterial disease for which
immunization was available. Large anthrax outbreaks in
humans have occurred throughout the modern era -- more than
6,000 (mostly cutaneous) cases occurred in Zimbabwe between
October 1979 and March 1980, and 25 cutaneous cases
occurred in Paraguay in 1987 after the slaughter of a single
infected cow. Anthrax, in the minds of most military and
counterterrorism planners, represents the single greatest
biological warfare threat. A World Health Organization report
estimated that 3 days after the release of 50 kg of anthrax
spores along a 2-km line upwind of a city of 500,000 population,
125,000 infections would occur, producing 95,000 deaths.
This number represents far more deaths than predicted in any
other scenario of agent release. Moreover, it has been
estimated that an aerial spray of anthrax along a 100-km
line under ideal meteorologic conditions could produce 50%
lethality rates as far as 160 km downwind. Finally, the
United States chose to include anthrax in the now-defunct
offensive biological weapons program of the 1950s, and the
Soviet Union and Iraq also admitted to possessing anthrax
weapons. An accident at a Soviet military compound in
Sverdlovsk in 1979 resulted in at least 66 deaths due to
inhalational anthrax, an inadvertent demonstration of the
viability of this weapon. The epidemiology of this inadvertent
release was unusual and unexpected. None of the persons
affected were children. Whether this is due to differences
in susceptibility between children and adults or purely to
epidemiologic factors (children may not have been outdoors
at the time of release) is unclear.
Anthrax is caused by infection with Bacillus anthracis, a
gram-positive spore-forming rod. The spore form of this
organism can survive in the environment for many decades.
Certain environmental conditions appear to produce "anthrax
zones," areas wherein the soil is heavily contaminated with
anthrax spores. Such conditions include soil rich in organic
matter (pH <6.0) and dramatic changes in climate, such as
abundant rainfall following a prolonged drought. Partly
because of its persistence in soil, anthrax is a rather
important veterinary disease, especially of domestic
herbivores. In addition to encountering anthrax while
grazing in areas of high soil contamination, these herbivores
may also acquire the disease from the bite of certain flies.
Vultures may mechanically spread the organism in the
environment. Anthrax zones in the United States closely
parallel the cattle drive trails of the 1800s.
Anthrax spores lend themselves well to aerosolization and
resist environmental degradation. Moreover, these spores,
at 2-6 microns in diameter, are the ideal size for impinging
on human lower respiratory mucosa, optimizing the chance for
infection. It is the manufacture and delivery of anthrax
spores in this particular size range (avoiding clumping in
larger particles) that presents a substantial challenge to
the terrorist attempting to use the agent as a weapon.
The milling process imparts a static charge to small anthrax
particles, making them more difficult to work with and,
perhaps, enabling them to bind to soil particles. This,
in part, may account for the relatively low secondary
aerosolization potential of anthrax, as released spores
bind to soil, now clumping in particles substantially in
excess of 6 microns. This clumping tendency, together with
a high estimated ID50 of 8,000-10,000 spores may help
explain the rarity of human anthrax in most of the Western
world, even in areas of high soil contamination. Other
potential bioweapons, such as Q fever and tularemia, have
ID50 values as low as 1 and 10 organisms, respectively.
continued...
http://www.medscape.com/govmt/CDC/EID/1999/v05.n04/e0504.16.cies/e0504.16.ci
es-01.html
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