The wake-up call in the US that led to greater security for materials that could be used in bioterrorism, including the anthrax bacterium, came not on 11 September but more than five years ago.

In 1995, Larry Wayne Harris - a registered microbiologist who the FBI says was a member of the white supremacist organisation Aryan Nations - was able to obtain the bacterium that causes bubonic plague.

The incident caused alarm and spurred reform, but even with post-reform restrictions in place, research institutions and laboratories say they are on a heightened state of alert.

The reforms have dramatically tightened regulations in the US, but biological weapons experts say that such controls need to be expanded internationally to ensure that some of the world's worst diseases are not turned into weapons of mass destruction.

Tighter regulations

In 1995, Larry Wayne Harris fraudulently applied to the American Type Culture Collection for the bacteria that causes bubonic plague. The ATCC is one of the world's largest collections of bacteria, viruses and DNA samples.

Harris pleaded guilty to a count of fraud and served an 18-month probation.

The US passed an anti-terrorism bill the next year requiring tighter regulations of biological agents that could potentially be turned into weapons.

The potential bio-weapons include 24 microbes and 12 toxins, including the deadly Ebola, Marburg and Rift Valley fever viruses, and the bacteria that cause anthrax and bubonic plague.

Organisations or individuals wishing to do research with these microbes and toxins must register with the Centers for Disease Control.

Applicants must prove that they have a legitimate need for research samples and they must open their labs to inspection.

Michael Powers with the Chemical and Biological Arms Control Institute says that there are also stringent requirements for labelling and for transport of the biological agents.

These help ensure that those applying for the organism actually receive it and so it is not intercepted in the process of transfer, he says.

Violators of the regulations can be imprisoned for up to a year and face fines up to $250,000 for individuals and $500,000 for organisations.

Loopholes

But even with these regulations in place, loopholes still exist.

Although the US Government has tried to tightly control manmade sources of these deadly agents, they still can be found in nature.

In 1998, Larry Wayne Harris and another man in Las Vegas were arrested for possessing anthrax. Harris's associate bragged that they had enough anthrax to "wipe out the city".

Harris said that he was able to grow the anthrax bacteria from tainted soil where infected cattle had been buried.

Harris would have required a lot of money to refine and develop the anthrax into an effective weapon, but he was in Las Vegas to buy millions of dollars' worth of laboratory equipment. Fortunately, the seller of the equipment was an FBI informant.

But Mr Powers says that although regulations have been strengthened in the US, there still is little agreement on international control regimes.

"The next step is to try to look at an international basis for trying to regulate against transfers of these particular pathogens," he said.

This is especially important with the admission by Russia that it had an extensive biological weapons programme.

Russia also has one of the last two known samples of smallpox, an agent that has the potential to be vastly more dangerous as a biological weapon than anthrax, Mr Powers says.

There has not been a case of smallpox since 1977. People lack natural immunity, and medical experts say that those inoculated against the disease have probably lost their acquired immunity.

The United States has been working with Russia in its Cooperative Threat Reduction Program to ensure that former biological weapons labs are either dismantled or converted to legitimate uses and that the scientists and technicians who worked in those facilities find legitimate work.

And Mr Powers says the 11 September attacks in the US could bolster efforts to expand international cooperation to limit biological weapons.

"What the attacks have done is to create a political environment that reinforces the need to undertake a lot of these measures to improve domestic preparedness and preparedness in other countries, to perhaps bolster the Cooperative Threat Reduction Programme and to harmonise international regulations to prevent the illicit transfers of materials, biological agents and equipment," he says.