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From the
January 2002 issue of
World Press Review
(VOL. 49, No. 1)
Science
and Technology: Anthrax and Bioterrorism
Trail of Terror
Debora
MacKenzie, New Scientist (weekly), London, England, Oct.
27, 2001
The cases just
keep coming. Yet it’s still not clear who’s to blame
for the anthrax attacks, or whether there will be more. With
little official information so far about the nature and origin
of the anthrax, claims and counter-claims have been flying.
Prominent voices in the United States charge that the anthrax
is so sophisticated it can only have been produced with the
backing of a government. Their suspicions are directed at Iraq,
which is known to have made anthrax and other bioweapons.
But New Scientist can reveal that the bacteria used in
the attacks is not a strain that Iraq or the former Soviet Union
mass-produced for weapons. In fact, it is either the same strain
the United States itself used to make anthrax weapons in the
1960s or close to it. Neither the strain nor the physical form
in which it has been sent out is particularly sophisticated,
say specialists.
What may matter more than the strain is how big a batch this
anthrax came from. This could reveal not only how many more
of these mailings we can expect but also whether the bacteria
were brewed in small-scale, makeshift labs or bigger facilities.
Work that could tell us is under way at a lab in the United
States. Crucial geopolitical decisions could rest on what emerges
from the electrophoresis gels and computer programs of the lab’s
small band of geneticists. Last week, Tom Ridge, President Bush’s
newly appointed Homeland Security adviser, stated that the anthrax
sent to Florida, NBC, and Sen. Tom Daschle were all the same
strain. An FBI spokesman in Florida confirmed the widespread
reports that this was the Ames strain.
But there has been confusion over what “Ames” means.
The name was given to a strain isolated at the U.S. Department
of Agriculture’s veterinary lab in Ames, Iowa, in the 1930s.
This strain, which was later shared with microbiologists around
the world, still strikes cattle in the western United States.
Recent American military research publications also mention
an Ames strain isolated from a cow in Iowa in 1980. However,
the scientists analyzing the anthrax from the attacks are comparing
its DNA with a library of strains collected from all over the
world. And in this collection, what’s called Ames has more
interesting origins. It emerged in the 1980s from a freezer
for the Center for Applied Microbiology and Research, the British
biodefense establishment at Porton Down, Wiltshire.
Porton Down acquired it from the U.S. Army Medical Research
Institute of Infectious Diseases in Maryland. It is, say those
who compiled the library, the strain the United States used
when it produced anthrax weapons. That program ended in 1969,
and the mass-produced anthrax was destroyed, although the United
States and its allies kept samples. To be identified as “Ames”
by these scientists, therefore, the anthrax used in the recent
attacks must either be the American military strain or one that’s
very similar.
So why choose this strain? “Ames is certainly a challenge
to any vaccine,” says Martin Hugh-Jones of Louisiana State
University at Baton Rouge. When lab animals immunized with the
vaccine now being given to thousands of American troops are
exposed to anthrax, many are still killed by the Ames strain.
Alternatively, the attackers may simply have wanted a strain
of proven virulence that’s hard to trace, says Ken Alibek,
former deputy head of the Soviet bioweapons program. “If
I were a terrorist, I would certainly not use a strain known
to be from my country,” he told New Scientist. The
Soviets did not mass-produce Ames, says Alibek. Nor did the
Iraqis. Like Britain in the 1940s, Iraq favored the Vollum strain,
isolated in Oxford in 1930, which has been identified in samples
from its Al Hakam plant. And the White House reiterated last
week that all anthrax mass-produced in the United States was
destroyed after 1969.
Despite this, Ames would not have been hard to find. Samples
of the weapons strain were kept in the United States and elsewhere.
Important clues also come from the size of the particles used
in the attacks. According to reports last week, they had been
milled down to a few micrometers, which is optimal for causing
the inhalation form of the disease. “The terrorists at
least had access to considerable know-how,” concludes Michael
Powers of the Chemical and Biological Arms Control Institute
in Washington, D.C. “This suggests some level of state
involvement.”
But Alibek dismisses claims that milling the powder this fine
is too hard for mere terrorists. His view is supported by a
secret experiment last year called Project Bacchus, in which
employees of the U.S. Department of Defense covertly produced
a kilogram of bacteria similar to anthrax. It was milled to
a few micrometers using machines available openly in the United
States.
Nevertheless, the attacks have caused relatively few inhalation
cases so far, which suggests that the spores were not blended
with the anti-caking chemicals used to promote airborne spread.
This is the secret of “weaponized” anthrax, says Alibek.
He says sending anthrax in the mail is a “very primitive”
way of distributing it and suspects the attackers don’t
have much material.
We could soon know. Paul Keim’s team at Northern Arizona
University in Flagstaff has pioneered the genetic analysis of
anthrax bacilli. Recently, says team member Kimothy Smith, they
have found that some DNA regions mutate frequently, as often
as once in every 1,000 cell divisions. Looking at which bits
of DNA have changed can also pinpoint the exact strain the unknown
anthrax came from. And that’s not all. A small batch of
anthrax will undergo many fewer cell divisions than a big batch.
Analysis could reveal whether the anthrax came from a 50-liter
fermenter of the kind Project Bacchus obtained or the huge vats
of a state-sponsored bioweapons facility. That could reveal
how big an operation the attackers had—and whether we must
expect yet more attacks. 
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