Issues Magazine

Bioterrorism – Being Prepared But Not Paralysed

By David Durrheim

Vast human migration, environmental disruption and trade have seen the recent emergence of many novel natural biological threats. Prevailing political, economic and ideological factors have increased the risk of unnatural microbiological events – bioterrorism.

The sky over the ancient city of Kaffa, on the Black Sea, was filled with pungent missiles. The attacking Tartar forces had resorted to catapulting the corpses of plague victims at the defending Genoese merchants.

This 14th-century siege marked the first recorded use of the most barbaric form of warfare and terrorism – bioterrorism. It has been hypothesised that the fleeing merchants transported plague-infected fleas and rats with them as their ships took flight, spreading the Black Death throughout Europe.

Unfortunately, this was not an isolated incident; there has been periodic heinous use of viruses, bacteria and their toxins to murder or disable individuals and their livestock, and to invoke terror in affected communities. Biological agents have been applied during formal warfare and also isolated terrorism incidents. In 1763, Lord Jeffrey Amherst, commander of British troops in North America, advocated the use of smallpox, writing: “Could it not be contrived to send the Small Pox among those disaffected tribes of Indians? We must on this occasion use every stratagem in our power to reduce them”. It appears that he indeed ordered the distribution of smallpox-infected blankets to the indigenous Indian population during the French and Indian Wars.

In 1984, an apparent politically motivated incident of bioterrorism resulted in 715 individuals developing gastrointestinal disease after two members of an Oregon sect contaminated a salad bar at a local restaurant with Salmonella typhimurium bacteria.

The most striking recent demonstration of the pandemonium that can result from a bioterrorism incident was the 2001 United States anthrax attacks. It took the form of anthrax spore-laced letters distributed through the US postal system. The attack is believed to have been domestically orchestrated by a scientist working in a government biodefence laboratory at Fort Detrick, Maryland, who committed suicide in 2008. Eleven cases of skin anthrax disease and 11 cases of inhaled anthrax disease resulted, with five of the latter victims dying. The attack resulted in consternation and panic seemingly disproportionate to the absolute threat posed, but this graphically illustrates the purpose of the bioterrorist: creating doubt, fear and social disruption, usually without forewarning.

During the 20th century, many countries developed the capacity to use biological agents to produce human and domestic animal casualties, and to damage crops or the environment. Although 144 countries adopted the 1972 Biological and Toxins Weapons Convention, which prohibits the development or acquisition of biological weapons, it is very likely that global adherence has not been complete.

Four agents are considered the most likely candidates for bioterrorism application based on their historical use, ease of distribution or potential for transmission between people, capacity to cause disease with a high death rate, ability to disrupt the public health system and likelihood that their release would cause public anxiety and social upheaval. They include two bacteria (anthrax and plague), a virus (smallpox) and a bacterial toxin (botulinum toxin).

Anthrax occurs worldwide as a disease of herbivores that become infected through contact with soil containing the spores of Bacillus anthracis. These spores persist indefinitely in the environment after contamination. Sporadic human cases occur in rural Australia after human skin contact with animals that have died from anthrax. A number of countries – including the US, the former Soviet Union (at least 68 people died after the accidental release of anthrax spores from a military microbiological laboratory at Sverdlovsk in 1979), the United Kingdom and Japan – are known to have developed anthrax as a biological warfare agent. If the spores are deliberately released in aerosol form they can cause severe pulmonary illness. Although effective antibiotics exist to treat this form of anthrax, unless they are immediately initiated, the disease can be rapidly progressive and fatal. The potential impact of an aerosol release of 50 kg of anthrax spores by an aircraft 2 km upwind of an urban population of half a million unvaccinated people could be profound, with up to 95,000 of those exposed succumbing if they are not rapidly treated.

Plague, which is caused by Yersinia pestis bacteria, mostly causes skin disease and swollen lymph glands (buboes) if infection occurs naturally following the bite of infected fleas. Generally this occurs when the fleas abandon dying rodents scavenging for food in human settlements following natural disasters or social disruption caused by conflict. The bacteria is found naturally on all continents except Australia and Antarctica. If released in aerosol form it can result in rapidly progressive pneumonia and sepsis, which is often accompanied by haemoptysis (coughing up of blood). Unless treatment with the correct antibiotics is promptly initiated, shock, multiple organ failure and death can result. A World Health Organisation assessment determined that, in a worst-case scenario, 50 kg of plague bacilli released as an aerosol over a city with five million inhabitants could result in 150,000 cases of pneumonic plague, with two-thirds of those affected requiring hospitalisation and up to 36,000 deaths.

Smallpox spreads between people, is stable as an aerosol, and only a small infectious dose is necessary to cause disease. The success of the smallpox eradication campaign, with the world declared free of smallpox in 1980, resulted in cessation of smallpox vaccination. Immunity has thus waned among those who have been vaccinated, while people born since 1980 have no immunity against smallpox.

Botulism is extremely rare in Australia but may be caused when food is contaminated with the Clostridium botulinum, which is found in soil. This bacterium produces a potent neurotoxin that causes paralysis of skeletal and smooth muscle. The affected person experiences rapidly developing and symmetrical descending paralysis, with prominent double-vision, speech and swallowing affectation, and impaired breathing. The botulinum toxin was first developed as a biological weapon over 70 years ago, and it can either be in aerosol form or used to contaminate food, with only a very small ingested dose required to kill a healthy human adult (less than seven-hundredths of a milligram).

The absolute risk of a bioterrorism attack in Australia is unknown. A national survey of Australian adults during 2004 found that about one-fifth of respondents considered the risk of a bioterrorism attack as high, while the remainder were equally split in perceiving the risk as moderate or low (http://www.racgp.org.au/afp/

200603/200603durrheim.pdf). The agents are available and lethal in small quantities that are relatively easy to conceal. Australia has aligned itself against fundamentalist ideological parties and states, thus increasing its likelihood of becoming a target. Thus there is no room for complacency; we must prepare for a possible bioterrorism attack as urged for by the Commonwealth Chief Medical Officer in 2002.

Effective surveillance is essential for early detection of a possible bioterrorism attack. Although traditional notification systems relying on laboratory reporting of confirmed diagnoses have served public health well, novel surveillance systems are necessary that can more rapidly recognise individuals or unusual clusters of individuals with signs and symptoms (syndromes) compatible with a bioterrorism agent exposure before a diagnosis is confirmed by the laboratory. Australian health authorities have invested in these early warning systems since the Sydney Olympics in 2000, and they can be used for detecting naturally occurring diseases like influenza pandemics, or bioterrorism-related events. In NSW, for example, a real-time emergency department system continually monitors syndromes of public health interest, while across Australia there is weekly community online surveillance for influenza-like illness (www.flutracking.net) that could be adapted for more frequent reporting of other syndromes.

An effective response to bioterrorism requires close collaboration between law enforcement agencies, postal services, health, ambulance and other emergency services. Because actual responses to hoax or real events are infrequently required, regular field exercises are necessary to ensure optimal performance of all aspects of the response. The success of these exercises should be publicised because only 19% of Australians in the 2004 survey expressed a high level of confidence in the government’s ability to cope with a bioterrorism event.

Australia has a good public health system, but thought should be given by the federal government to either stockpiling or ensuring rapid access to ventilators and appropriate antibiotics for treating people infected with bioterrorism agents or preventing illness in individuals after a suspected exposure. Australia’s laboratories must maintain the capacity to rapidly confirm or exclude bioterrorism agents when clinically suspected.

There is a need to further refine the vaccines available against the principal biological threats. This should, however, not be at the expense of improving immunisation coverage globally, with routine vaccines for children most at risk. More than three million children under five years of age die each year due to diseases against which we already have effective and safe vaccines.

The national survey found that if people thought they had been exposed to a bioterrorism agent, 59% would first seek diagnosis and care from their doctor and 33% from their local emergency department. Doctors in general practice and emergency departments must therefore be prepared to recognise presenting symptoms of bioterrorism agents, treat patients promptly and raise the alarm.

The Australian government should continue to advocate strengthening the Biological and Toxins Weapons Convention, in particular demanding an enforceable protocol that includes verification and compliance provisions.

Media communication in response to the 2009 influenza pandemic oscillated violently between balanced and accurate, and alarmist or inappropriately reassuring. Inappropriate risk perceptions can cause considerable damage to community well-being or to the strategies put in place to limit harm.

Although GPs were also noted by many Australians (22%) as their preferred source of reliable information during a suspected bioterrorism attack, print and broadcast media (25%), the internet (18%), hospitals (11%) and the government (11%) were all frequently mentioned. Accurate and timely information needs to be available through each of these communication portals, including clear advice on how to minimise personal and community risk.

Bioterrorism is a terrible reality of ancient origin. The 2001 anthrax attacks in the US may be a precursor to even more diabolical attacks, but we do not know when.

Fortunately, we can do a lot to prepare to detect and respond promptly to these incidents and thus limit their potential catastrophic harm. We will then also be prepared to detect other emerging infectious disease risks and better respond to natural disasters.

Attempts should continue to secure a safer future through greater international social justice investments and enhanced legal conventions.