The Truth about Anthrax

The word alone is enough to strike fear into any heart - and never more so than today. Yet much of the anxiety we feel about the world's most notorious biological weapon is based on myth and misunderstanding. Steve Connor separates fact from fallacy

It starts with a light aircraft, flying upwind over a major city, perhaps London or Washington. From below, people in the street notice a fine mist emanating from the undercarriage, like some crop-dusting scene from an old movie. Perhaps they think no more of it, and the hours pass without further incident or obvious effects.

But then, some days later, the first symptoms appear. The first sign is a sudden onset of the chills among the people who were out on the streets that day. That is soon accompanied by a splitting headache and a high fever. Before long, nausea has progressed to vomiting, stomach pains and a rapidly falling pulse, with a subsequent loss of blood pressure.

Those who know a little about such things realise now that they are witnessing the classic symptoms of toxic shock. But while anthrax may begin like an attack of flu, the end is far more serious and frequently fatal. Before long, many of those who heard the plane's distant humming will be dead. And when the news breaks, millions more will be living in panic. For as a weapon of biological terror, the microbe Bacillus anthracis is second to none.

In 1993, the US Congress Office of Technology Assessment estimated that the release of just 100kg of anthrax spores over Washington, DC – equivalent to the weight of one large man – would, in the right wind conditions, result in the deaths of about three million people. Everyone is now wondering, in the light of the terrorist attacks in America and the death from anthrax of a Florida journalist at the weekend, whether someone else has been making similar calculations.

Anthrax has long been considered the likely weapon of choice in the nefarious world of biological warfare – a world supposedly outlawed by international agreement, although of course few terrorists abide by treaties. For, in addition to being lethal, the anthrax bacterium can easily be grown into sizeable doses. And, with its natural tendency to form highly stable spores, it can be stored almost indefinitely, either as a watery paste or as a dry powder. Although it is essentially an animal disease, anthrax is also lethal to humans. There is, however, no evidence that it is "infectious" in the sense that it can be transmitted from one person to another. The fact that man is a "dead-end" host of the disease is another reason why military planners have historically flirted with the idea of using the agent in a biological attack.

During the Second World War, Britain had its own secret biological weapons programme involving anthrax, when it believed that the Nazis were planning something similar. In a test that was to become notorious, scientists exploded a number of anthrax bombs on the remote island of Gruinard, south of Ullapool, off the west coast of Scotland. Gruinard had been requisitioned in 1942 and declared a prohibited area – a status that was to remain in force for another 50 years. Indeed, when I was there as a guest of the MoD in 1986, so real was the continued threat of infection that I had to wear plastic overalls – nicknamed Noddy suits – from head to foot.

Military scientists who took part in those tests discovered something that is now well established in the annals of biological warfare: that anthrax, like any biological weapon, makes little sense in regular military terms. Quite apart from any moral objections to using an agent that kills in such an indiscriminate and appalling manner, anthrax weapons are inherently unpredictable. Their effects are difficult to contain and control, and, most important of all, the agent itself is almost impossible to deliver with any accuracy or guarantee of effectiveness.

But Gruinard proved something else, too: that it is extraordinarily difficult to get rid of anthrax spores once they are in the ground. Even 45 years after the experiment took place, spores on Gruinard were still capable of causing disease. In the end, it took constant spraying with a solution of formaldehyde and sea water over a period of many weeks, using 30 miles of perforated tubing, to rid the island of its biological pest.

Yet the reasons why a military superpower might reject anthrax are precisely why it becomes so attractive to a terrorist organisation or state. The real terror of anthrax comes not so much from its potentially devastating impact, but from the panic that such a threat creates in the public at large.

According to Professor Harry Smith, who headed a Royal Society investigation of biological weapons published last year, it is this fear that makes anthrax so attractive to terrorists. "Unlike nuclear, chemical or high-explosive devices, biological weapons have never been shown to be effective in the field of war or terrorism," he says. Professor Smith, who also led Britain's investigation into the military uses of anthrax while at the Porton Down research establishment between 1947 and 1964, adds: "What might happen from an anthrax attack is to a great extent conjecture."

Professor Smith points out that the US Office of Technology Assessment based its 1993 estimate of three million deaths from an anthrax attack on lethal experiments involving monkeys, which he says are more susceptible to anthrax than humans. "So the judgement on whether an anthrax weapon is effective is actually not proven," he argues. "If anyone actually did this, however, it would undoubtedly cause panic, and panic is the main danger coming from these organisms."

What is known about anthrax indicates that it is a more difficult disease to catch than many people realise. To kill effectively, terrorists would aim to release enough spores into the air to cause death by inhalation. But respiratory anthrax can be caused "naturally", too, most commonly in mills that handle animal hides – and studies in this area show just how difficult it is to cause infection by this route.

For instance, in the 1950s, only about 50 to 60 cases of anthrax occurred on average each year among American millworkers who processed animal hides and hair contaminated with the spores; and, of those infections, only one in 20 was caused by inhalation of spores, the rest being made up of the far less dangerous cutaneous form of the disease, caused by spores infecting the skin rather than the lungs.

"It seems that humans do have at least some resistance to anthrax," Professor Smith continues. "Although it is important not to underestimate the danger, it is equally important not to exaggerate it."

There is, however, one instance in which inhalation of anthrax spores did cause widespread loss of life: in the former Soviet Union in 1979, at a secret military installation at Sverdlovsk (now Ekaterinburg), which is now thought to have been experimenting illegally with the disease. At least 64 people are known to have died after the accident, and at least 1,000 more are thought to have been hospitalised. The Soviet authorities, presumably mindful that the production of anthrax weapons would be tantamount to a breach of the Biological Weapons Convention 1972, repeatedly lied about the incident. For years, the Soviet government claimed that the outbreak was the result of a batch of contaminated meat being processed and sold illegally. Indeed, an official report published in May 1980, a year after the outbreak was first reported, claimed that all the cases could be put down to diseases consistent with eating or handling infected meat.

Conveniently, the hospital records of the victims went missing, so there was no way of disputing the findings at a later date. However, two of the pathologists involved did manage to keep tissue samples from 42 patients who died in the outbreak. Their analysis of the preserved lung tissue indicated respiratory anthrax, and their report, published in 1993, said that the victims had in fact died as a result of inhaling anthrax spores.

The Sverdlovsk incident was one of the most serious outbreaks of respiratory anthrax and clearly demonstrated the lethal nature of an aerosol spray loaded with the spores of the bacterium. Yet, given that the military facility alone employed about 15,000 people, and that a residential area housing many thousands more was exposed to the aerosol, it is perhaps surprising that there were so few reported deaths.

"It must be remembered that anthrax is like any disease," says Professor Smith. "Not all exposed persons will become infected, not all infected persons will develop the disease, and not everyone who gets the disease will die as a result."

But although anthrax seems not to be as dangerous as the terror it creates, that may not always be the case. There are genuine fears that scientists working for a terrorist state may one day be able to tinker with the bacterium's genome in such a way as to change its lethality. "I can easily conceive that anthrax could be made antibiotic-resistant, if someone set their mind to it," says Professor Smith. "Theoretically, it could also be made to be more infective, although this would be harder."

At present, it takes about 2,500 spores to infect a person by inhalation, but genetically modified anthrax could feasibly be far deadlier, requiring just a few dozen spores wafting about in the air. Another theoretical goal would be to create a strain that could pass from person to person, making an uncontrollable epidemic at least plausible. Iraq is one of several countries in which such inexpensive research could be carried out, Professor Smith says.

But even without such research, the real terror of anthrax is here already. It is a terror fuelled not so much by the actual risk it presents, but by our often misguided perception of what that risk is.