After decades of neglecting the threat from "regional aggressors" - Third- World powers - armed with biological weapons, three events have reinforced international concern. These are: the discovery of Iraq's arsenal after the 1991 Gulf war; evidence that Russia continues to develop deadly viruses and bacteria; and the threat that terrorists like the Aum Shinri Kyo cult in Japan, which used nerve gas in the Tokyo underground, might turn to these horrific bugs, which can be grown as easily as brewing home-made beer.
"Preventing determined proliferators acquiring biological and toxin agents appears to be virtually impossible," the IISS concludes. Whereas large- scale attacks are unlikely in the near future, it says, "these barriers are crumbling and the revolutionary advances in biotechnology will probably remove them altogether in the first decade of the 21st century".
Biological weapons use micro-organisms - either bacteria or viruses - or toxins which, although biological in origin, behave more like deadly chemicals. Weight for weight, biological warfare agents can be hundreds or thousands of times more potent than chemicals, and can cause a variety of symptoms.
Aum Shinri Kyo experimented with anthrax, which causes breathing difficulties, exhaustion, toxaemia and cyanosis and kills in 95 to 100 per cent of cases but, fortunately, their experiments affected no one. Anthrax is probably the deadliest biological agent: others which have been developed are tularaemia (deadly in 30 to 40 per cent of cases), botulism and bubonic plague.
Despite continuing inspections by the United Nations, it suspects that Iraq continues to retain biological weapons. The IISS report says inspectors found Iraq had developed biological rocket warheads.
Although the design was crude - each rocket carried about eight litres of liquid anthrax spores or botulinum - one rocket could contaminate several square kilometres. Iraq also developed biological fillings for 155mm artillery shells and aircraft bombs, and had come close to developing spray tanks.