Bioterrorism only beaten by preparation and understanding

It is 30 years since the world saw the last case of smallpox, the last natural case occurring in Somalia in 1977. The eradication of smallpox represents one of the great triumphs of preventative medicine and international co-operation in recorded history.

Wiping out smallpox broke one of history's longest chains of disease transmission, stretching back more than 3,000 years. In the 20th century, smallpox caused between 300 and 550 million deaths, three times the number in all wars during the century.

The feat of conquering the disease was based on widespread vaccination supported by active surveillance schemes, and that success raised the profile of public health. It ushered in a period of active public health campaigns aimed at a variety of infectious diseases.

Australia has been no stranger to smallpox, and the disease was a frequent visitor to our shores until the early part of last century. The epidemic that raged among the Aboriginal population in 1789 and surfaced regularly until the late 1860s remains probably the only example of a major demographic crisis in Australia's history. The last major outbreak of smallpox occurred in New South Wales in 1913-17, when more than 3,000 people caught the disease.

What relevance does smallpox hold for us today? For the generations born since vaccination, it remains a distant memory associated with parents or grandparents. For those of us vaccinated in the past there is the belief (untrue as it turns out) that we had been granted a lifelong immunity to the disease.

Smallpox, along with other biological agents, is once again in the spotlight due to concern about the possibility that an illicitly obtained supply of the virus could be deliberately released.

In 2004 the Australian Government produced a management/response plan for just such an event, and while bird flu and the threat of a pandemic of influenza have pushed bioterrorist events into the background, the threat remains.

A survey of 1,001 Australians in 2004 indicated that more than half thought that a bioterrorist event in Australia was of medium to high concern, and of those not previously vaccinated against smallpox many expressed a strong willingness to accept vaccination as a precautionary measure in the absence of a bioterrorist event.

No one really knows what became of the tens of tonnes of modified smallpox virus that was part of the Soviet biological warfare program up until the early 1990s, or what became of many of the thousands of scientists working on this program. Other nations are thought to have secret stocks of the virus.

The sarin release by a Japanese cult in 1995 and the anthrax incident in the US some years later indicate the ease of obtaining, modifying and releasing biological agents into unsuspecting populations. But we should not exaggerate this threat. "Rogue'' states or bioterrorists seeking to acquire and use smallpox as a weapon would have to overcome some fairly significant obstacles.

These would include the need to grow the virus in eggs or human tissue, and finding an effective way to disperse the virus into a vulnerable population. But in the unlikely event of such a bioterrorist release of smallpox in Australia, how well are we prepared?

The backbone of preparedness is an excellent system of surveillance and response involving the ready availability of an accessible and safe vaccine, and a healthcare and emergency system that can respond in a timely manner.

Probably Australia would need between 2 and 5 million doses of vaccine to feel safe. Currently we hold between 500,000 and 1 million doses of the old live virus. But regardless of how many doses we currently hold, who would we deliver it to, where and how? These are important questions.

Given a single occurence or cluster of smallpox cases, the timely delivery of vaccine becomes a priority. Also, given the wave of public reaction, fear and hysteria that we might expect to result, would not the public overwhelm the vaccination depots set up and would not the "worried well'' overrun local GP practices? This certainly happened in the past, and simulation exercises in the US suggest that it could happen again.

How would we manage this human reaction? To do so we need to enter the frame of reference of the average citizen and understand how they see risk and how this differs from how experts see risk. And who could we expect to be vaccinated? Key medical and emergency workers certainly, but who else? The current management plan suggests a "ring fencing'' campaign, where cases and immediate contacts would be vaccinated. But given that smallpox has an incubation period of up to 17 days, and that people move around a lot, how easy would tracing contacts prove?

And what about the impact on our healthcare facilities? Again the management plan discusses establishing "care centres'' - quarantine hospitals? - which would be established in key locations. There seems little doubt, however, that existing healthcare facilities would be pressed to the limit.

Hopefully, a bioterrorist event will never happen in Australia, but if ever it does, we need to be assured that we are properly prepared and fully understand all the issues.