Anthrax in the US: many unanswered questions, but lessons nonetheless

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The anthrax outbreak in the US has put many on edge about biological warfare and ‘bioterrorism’. Anthrax has killed four people and made 13 others ill since it appeared in the US in late September. Dozens have been exposed to the spores without becoming infected. According to the US Centres for Disease Control and Prevention, about 32,000 Americans have started taking antibiotics. Environmental tests reveal that no branch of the US government, including the Supreme Court, state department, CIA and congress, as well as numerous mail-processing centres and offices, were touched by the scare. Some white powder discovered in the office of a British Petroleum joint venture in Ho Chi Minh City, Vietnam, has also tested positive for anthrax spores.

Anthrax (Bacillus anthracis) is a livestock pathogen most commonly found in sheep. Spores also occur in the soil of rural areas, where they can survive for decades. Normally spores in the soil do not affect human beings because they do not come up from the ground in significant quantities and a few spores cannot cause infection. Wool-sorters inhale anthrax spores in small quantities continually, and become ill rarely.

Studies have shown that between 8,000 and 10,000 spores are required to make one LD50, that is a lethal dose capable of killing 50 percent of infected humans. According to the London-based Jane’s Defence Weekly (May 1, 1998), “anyone exposed to at least 20 anthrax spores per cubic liter of air for about 30min will probably receive close to an LD50 dose.” Inhaled spores attack the vulnerable lung tissues, where the spores can easily vitiate the immune system’s response. It can also invade the body by other routes, such as skin-cuts and the stomach lining (from undercooked meat).

The continued mystery has made the US authorities seem helpless and defensive. About two months after the anthrax-tainted letters began to arrive, authorities say that they still know almost nothing about where the powder comes from or who made and sent it. Nothing reflects this confusion more than the array of theories about the spores’ source. Some theories, advanced mainly by hardliners in the Bush administration and the media, betray a desire to whip up hysteria and implicate a convenient scapegoat. One such theory postulates a link between the perpetrators and Saddam Hussein’s regime. Another accuses Usama bin Ladin and al-Qa’ida or some other small radical group. The “garden variety” theory claims that the anthrax-tainted letters could have been sent by educated amateurs, perhaps even a loner with a PhD in microbiology, with access to special equipment, techniques and expertise.

The letter opened in Senator Tom Daschle’s office on October 15 has attracted the most attention from experts. Tests conducted at the US Army Research Institute of Infectious Disease at Fort Detrick, Maryland, revealed that the powdered anthrax contained in the letter had been aerosolized: the powder was milled to the right size and mixed with silica, a mineral that prevents the particles from clinging together, allowing them to float in the air and lodge in the lungs.

Yet fears that the hidden hands of Saddam Hussein, Usama bin Ladin or a small radical group lurk behind these attacks fail the test of close scrutiny. The anthrax strain used in the letters, the Ames strain, does not suggest an Iraqi connection. The Ames strain is native to the US and not known to have been turned into a weapon by any major state-sponsored biological-weapons programme, although Iraq is believed to have tried to obtain it in the late 1980s. Iraq used a strain known as Vollum, obtained from the American Type Culture Collection (Rockville, Maryland) in its anthrax weapons. The evidence is that Iraq’s anthrax stockpiles were not in dry but in liquid form. UN inspectors have found only two Iraqi warheads containing liquid anthrax, which renders the spores ineffective because the liquid tends to form globs that fall to the ground instead of floating in the air. By contrast, the inspectors found hundreds of warheads containing mustard gas and nerve agents, which tend to diffuse uniformly through the air. That leads to the question of why Iraq would load its missiles with liquid anthrax if it were able to produce dry powdered spores.

According to Scott Ritter, former UN weapons-inspector in Iraq from 1991 to 1998, “Iraq’s biological weapons programmes were dismantled, destroyed or rendered harmless during the course of hundreds of no-notice inspections” (the Guardian, October 19, 2001). Even if Iraq has not complied fully with the disarmament demands of various UN resolutions, tests on thousands of swabs and samples taken from soil and facilities throughout Iraq have yielded no evidence that Baghdad retained biological weapons or production equipment.

The “small group” and “garden variety” theories picture the anthrax being produced in a crude lab in a cave or somebody’s garage, basement or back yard. Proponents argue that samples of anthrax bacilli could have been stolen from any one of hundreds of labs and then processed to make a liquid broth, using equipment purchased by mail from any laboratory supply house. But the process of producing “weaponized” spores is beyond small groups, never mind lone amateurs, using stolen laboratory cultures. According to Gary Novak, an independent mushroom physiologist, bioweapons cannot be produced using laboratory strains of microbes: “microbes undergo rapid attenuation under laboratory conditions, because repeated transfers on culture media results in rapid genetic drift, as adaptation to laboratory conditions occurs.”

An anthrax factory set up in a populated area would need sophisticated containment systems. Without these extremely costly safety measures, spores would spread easily through the vicinity, causing an anthrax outbreak. Equipment would need to be cleaned by a complicated process that involves enclosing it in a pressure chamber and steam-sterilizing it for several days, an operation with an estimated cost that runs into hundreds of millions of dollars. Drying the liquid into a fine powder of pure spores that can be inhaled is also well beyond the capabilities of small groups or amateurs. It requires rare expertise and specialized processing equipment, including spray dryers, grinders and enormous centrifuges. Reducing the spores successfully to particles of the required weapons-grade size of 1 to 5 microns involves sophisticated techniques and equipment: the bacteria are fragile and thermolabile (i.e. unstable when heated). Without the proper equipment, the spores would coalesce into large clumps that would be dragged rapidly to the ground by their weight, instead of remaining suspended in the air.

There has also been concern that the powder sent in the US mail might have come from Russian anthrax that found its way onto the black market after the fall of the Soviet Union. The Soviet Union’s biological-weapons programme produced genetically engineered antibiotic-resistant strains of anthrax believed to be deadlier than any other existing form. It also developed a “vacuum drum drying” method of producing anthrax powder with an annual output estimated at 4,500 metric tons. However, the powder sent to US government offices and news media was not genetically engineered for exceptional virulence or resistance to antibiotics; indeed it is rather “antibiotic susceptible.” Spores found in Daschle’s office (New York) and in Florida were indistinguishable: all were of the Ames strain, and treated with a high-grade additive using a technique known only in the US.

All this points strongly to the “home grown” theory, which suggests that the blame being pinned on outsiders is misplaced. More importantly, it directs attention to the question of stocks of chemical and biological weapons in the US. Officially the US destroyed its biological stockpiles in 1969. In 1972 the US announced that it had unilaterally stopped military research into offensive biological and toxin warfare, and production stocks were supposedly destroyed.

The recent anthrax cases underscore the limitations of arms-control in eradicating the scourge of biological weapons. Even if one were to take the claims of successive US administrations about the destruction of American stockpiles at their face value, it is not clear whether “seed stocks” (from which new batches could be grown) met the same fate. The international biological-weapons treaty does not forbid signatories to produce small numbers of biological weapons for “defensive research.”

This outbreak brings home the importance of a change in modes of thinking: away from the conventional wisdom that biological weapons pose “battlefield” problems; towards an awareness of vulnerability elsewhere. From now on biological weapons will haunt humanity. Life in the 21st century may be fraught with more disquieting possibilities than those of a thermonuclear conflagration.

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