Sowing plague from the skies

Germ warfare is emerging as a chilling new terrorist threat. ANDREW LAXON reports.

The scenario: terrorists use topdressing planes to spray deadly chemicals or biological diseases across a country, killing thousands - perhaps millions of people.

A few weeks ago the idea would have been laughed off as theoretically possible but difficult, dangerous and extremely unlikely.

Experts say it still is, mainly because terrorists would find other methods easier and more effective.

But since September 11, when hijackers took over airliners with box-cutting knives and sent them crashing into the World Trade Center and the Pentagon, killing nearly 7000 people, nothing looks so far-fetched any more.

The germ warfare threat has been taken increasingly seriously this week, with revelations that the hijackers were trying to learn to fly topdressing planes.

The news has already forced the World Health Organisation to rush out an early draft of a report warning Governments to be on their guard against biological and chemical weapons and advising on precautions.

Were the hijackers really planning to launch biological or chemical attacks from topdressing planes?

It looks increasingly likely.

Alleged hijack leader Mohammed Atta and two other hijackers spent six to eight weeks visiting a topdressing business every weekend.

South Florida Crop Care staff said the hijackers persistently asked odd questions about the blue and yellow 502 Air Tractor cropduster. They wanted to know its range, what quantity of chemicals it would take, how difficult it was to fly and how much fuel it carried.

One said Atta repeatedly asked to see the interior of the cockpit and asked how to start the planes.

The hijackers had a topdressing manual and had downloaded a large amount of information from the internet on aerial application of pesticides.

Investigators are still not sure whether the cropdusting plan was a backup to the suicide attacks or a separate operation, which may still be under way.

All topdressing planes across the United States were grounded for two days but the ban was lifted yesterday.

What would the hijackers have sprayed from the plane?

No one knows, but the main biological possibilities are anthrax and smallpox - the two diseases authorities fear most - as well as botulism and bubonic or pneumonic plague. Chemical weapons include mustard gas, sarin and its more lethal variant VX.

Anthrax is the size of a speck of dust and can infect humans through touch, inhalation or broken skin. After an incubation period of one to six days, it produces high fever, fatigue and coughing. Ninety per cent of its victims die, usually within two to three days. It can be treated with antibiotics, including penicillin, or prevented by vaccination. It is not contagious.

In contrast, smallpox spreads rapidly and easily between people, killing about 30 per cent of its victims. The airborne virus was supposedly eradicated in 1980, with only small quantities held in laboratories for scientific purposes in the United States and Russia.

However, experts believe Russia, Iraq and North Korea have all experimented with smallpox. There are reports that Russia used genetic engineering to try to make both smallpox and anthrax more lethal and resistant to antibiotics and vaccines. The United States had a similar programme, which is now on hold.

What about chemical weapons?

Mustard gas has been used from the First World War to the Iran-Iraq war of the 1980s. When inhaled, it causes painful blisters all over the body, as well as chronic lung damage, blindness and cancer. A gasmask is the best protection.

Terrorism experts are more concerned that the terrorists might have been using sarin or its refined version, VX. Sarin was developed but not used by Germany in the Second World War and is probably still held by Iraq, which used it in the war against Iran. The Japanese cult Aum Shinrikyo used it to kill 12 people in a Tokyo subway in 1995.

Sarin is a highly toxic gas that attacks the central nervous system. The more lethal VX can kill with a 10mg dose - one tenth the amount required for sarin. It can also be absorbed more easily through the skin, which is why investigators were so worried when they first found the hijackers' topdressing manual.

Would the plan have worked?

Not according to most topdressing and terrorism experts. South Florida Crop Care manager Willie Lee calls the use of his planes by terrorists "far-fetched".

"You've got to be well schooled to even crank up a cropduster. Why would you go to the trouble of getting into an aircraft you don't know when you could load it [the chemical] into a truck and do the same thing?"

His business is based in Belle Glade, in the heart of a sugar-growing area of hundreds of thousands of hectares near Lake Okeechobee, a water source for millions in Florida.

Locals now wonder whether cropdusters could be used to contaminate food or water supplies.

"Our view is that it would be difficult. Certainly we can't spray any gas," says James Callan, executive director of the National Agricultural Aviation Association. "Any volatile liquid, how would that be loaded?"

Dr Peter Katona, a UCLA professor of clinical medicine who helps Los Angeles County with its anti-bioterrorism programme, says an attack on a major water supply by crop-dusters was unlikely because the terrorists would need to drop huge quantities of chemicals.

So is any kind of aerial spraying attack likely to succeed?

"In terms of concept, it is a potential means of disseminating a biological or chemical weapon," says Frank Cilluffo, chairman of the Committee on Combating Terrorism at the Centre for Strategic and International Studies.

"But this method could be limited. It may not have the effect intended."

About 5000 "agricultural aviation" planes operate in the United States, many of them small, single-engine propeller aircraft that carry about 2000 litres of pesticide or fertiliser, according to the National Agricultural Aviation Association.

Bioterrorism experts have frequently cited cropdusters as a threat because they are used to dust large land areas - up to 200 hectares with a single load, say pilots - and can fly below Federal Aviation Administration radar coverage.

However, the fact that topdressers scatter chemical or biological agents to the wind makes them inefficient compared with other primary bioterror delivery methods - using humans or missiles as carriers, says Cilluffo.

"Its effectiveness depends on a whole host of factors, including atmospheric conditions ... It makes this, in my eyes, a more rudimentary mode of delivery."

Bioterror experts say no one is sure if anthrax, smallpox or other likely agents would survive an airdrop in sufficient strength to cause damage.

An assault on a sports stadium hosting 50,000 people is also thought unlikely because victims of such a public assault could be treated immediately.

"If you do it covertly, in, say a convention centre, nobody is going to know until people start showing up at emergency rooms days later," says Katona.

"It is more likely that they would strike more covertly."

Terrorists also might decide that such attacks would fail to provide the psychological horror they sought.

"Explosives are more familiar to the people committing these acts," Katona said. "[Chemical weaponry] is not as graphic a television image."

But he adds: "When you have what happened on September 11, all bets are off."

Should we be taking precautions?

"We don't recommend that people walk around breathing through handkerchiefs or masks," says Dr David Heyman, head of communicable diseases at the World Health Organisation.

"The best defence is strong disease detection. A good public health system is the best investment any country can have."

Despite Heyman's advice, germ warfare panic appears to have broken out in Britain and the United States already.

The Independent reports a run on gasmasks and chemical protection suits at army surplus stores, with one wholesaler claiming he has sold 2000 masks to shops this week, compared with about 20 normally.

Is vaccination the answer?

Hayman says the WHO is trying to confirm where vaccine stores are held against some of the biological weapons which could be released.

It is also encouraging Governments to ensure adequate stocks are available.

But mass vaccination once an outbreak of a disease like smallpox had begun would be too late.

Older people who had been vaccinated against smallpox might have enough protection to reduce the impact of the disease but not to prevent it.

Unofficially, the answer seems to be that we hope it doesn't happen. The WHO report on biological and chemical weapons predictably urges countries to have a contingency plan in case of attack.

But, perhaps more realistically, it adds: "Managing the consequences of a deliberate release of biological or chemical agents may demand more resources than are available. International assistance could become essential."

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