Anthrax is an acute infectious disease caused by a bacterium, Bacillus anthracis, which can form highly resistant spores that can lie dormant in the soil for many decades. It has been extensively investigated as a potential biological weapon by Britain, America, Iraq and the former Soviet Union, although it has never been used in open warfare.
Anthrax is primarily a disease of animals but it can also infect humans by one of three routes, none of which results in an infected person being a danger to others. In other words, anthrax is not a highly infectious disease which could be seen as an advantage on the battlefield.
However, as a terrorist weapon its power lies in the ability to cause mass panic. A relatively small sample of powdered anthrax spores could cause chaos if released on a city's underground network and would involve expensive decontamination.
Cutaneous anthrax is caused when the bacteria or its spores infect a victim's skin. The first symptoms include raised, itchy bumps, much like the red marks caused by an insect's bite. Skin vesicles and painless ulcers develop within a couple of days of exposure. This form of anthrax is easily treated with antibiotics, but without treatment, about one in five infected individuals will eventually die. This form of anthrax was once prevalent among mill workers handling animal hides and hair.
Another form of anthrax is intestinal, caused when someone eats infected meat. Initial signs are nausea, loss of appetite, vomiting and abdominal pain. Between 25 and 60 per cent of patients die of this form of anthrax unless treated with antibiotics.
Pulmonary anthrax is the most feared form of the disease, caused by breathing in the bacterial spores. Initial symptoms are a mild, flu-like fever but within days the infection can lead to breathing difficulties and toxic shock resulting from a catastrophic fall in blood pressure. Without treatment, between 80 and 95 per cent of people with pulmonary anthrax will die. However, victims need to inhale between 2,500 and 10,000 spores before an infection can take hold and swift treatment with antibiotics can prevent death.
In the former Soviet Union in 1979, 64 people died from pulmonary anthrax after breathing in spores from a secret bioweapons facility at Sverdlovsk (now Ekaterinburg). The Soviet authorities claimed it was an outbreak of intestinal anthrax caused by contaminated meat, until a 1993 investigation showed it was pulmonary anthrax.