Special feature: Bioterrorism

Bioterrorism is the term used for terroristic activities in which biological substances are used to cause harm to other people. What is terrorism? (Source: Federal Emergency Management Agency). Bioterrorism is a combination of biological warfare and terrorism and due to the events in the world bioterrorism is currently receiving a lot of attention. A publication by the National Strategic Forum on Mitigating the Effects of Chemical and Biological Attack (Dec 1999) is still extremely relevant today (Source: Inst. for Natuional Strategic Studies).There are a number of diseases that can be used as a weapon. There are two scenarios that are currently seriously dreaded. One is the spread of an infectious disease through the air, the other is the contamination of drinking water. It is not at all easy to choose a biological weapon or to produce one. People have lived with diseases for ages, and have learned to cope with many. Our body has inborne defenses against diseases, and during life we have been exposed to many diseases, and become immune to a number of them. See our exhibit on 'pathogens' to learn about bacteria that cause disease. Our exhibit on 'pathogenicity' explains some of the properties that bacteria have to cause disease. Finally, our immune system is explained in a separate exhibit. So what are the requirements for a serious biological weapon to spread through the air?

The disease must be severe and apparent within a short time: it must have a short incubation time
it must be able to cause disease by inhalation
it must be possible to produce the causative agent in large amounts at minimal risk.

This excludes a number of diseases that have a long incubation time, are not severe enough, or to which a majority of the population is immune (due to natural occurance or vaccination programs, such as measles or tetanus). In general, viral diseases are unpractical to produce as a weapon, since viruses can only reproduce inside a body or inside a cell under laboratory conditions. This makes the production of viruses expensive, technically difficult and tedious. In the past, there have been experiments with smallpox (a virus which has been eradicated by world-wide vaccination but which is still stored by a few registred laboratories). To work with small-pox, people have to protect themselves to the highest possible degree, see this picture of Biosafety Level 4 containment (Source: CDC). The same is true for the deadly but very uncommon viral diseases such as hemorrhagic fevers (Fact sheet) (Source: CDC). For this reason such diseases are unlikely to be used as a weapon. But we can not rule out anything. Read about the possibility of small-pox as a biological weapon (Source: Center for Civilian Biodefense Studies)

Bacteria are easier to produce than viruses. Therefore bacterial diseases are the most dreaded. There are only certain bacteria able to cause disease after inhalation.The diseases they cause must be severe but uncommon, so that not many people are immune. The lethality of a biological attack has been compared to that of a nuclear attack. See this graph of casualties (Source: CDC). Only a few diseases are seriously considered as potential weapons for bioterrorists:

Anthrax, caused by Bacillus anthracis.

Learn more about this bacterium and its disease from this fact sheet on Anthrax (Source: CDC)
Read about the use of anthrax as a biological weapon (Source: Center for Civilian Biodefense Studies)
Use our species file on Bacillus anthracis for more on-line information.
See the Consensus statement on the recommendations for measures to be taken by medical and public health professionals following the use of anthrax as a biological weapon against a civilian population (JAMA 281:1735-1745, 1999)
The American Anthrax outbreak of 2001 (UCLA Dept. Epidemics).

Plague, caused by Yersinia pestis

Learn more about this bacterium and its disease from this fact sheet on Plague (Source: CDC)
Read about the use of Plague as a biological weapon (Source: Center for Civilian Biodefense Studies)
Use our species file on Yersinia pestis for more on-line information.

Tularemia, caused by Francisella tularensis

The reason why F. tularensis is a candidate weapon is that 5 organisms can already be lethal when inhaled, as described in this Data Sheet (Source: Health Canada)
Read about t he use of Tularemia as a biological weapon (Source: Center for Civilian Biodefense Studies)

With these organisms experiments have been carried out to investigate how 'suitable' they are to be used as a weapon. They were found remarkably suitable, though there remain severe practical problems, mainly with the mode of spreading/spraying (to be effective the organisms have to be spread in a fine mist of aerosols), and the weather (humidity, wind, temperature) strongly influences the effects. These 'natural enemies' of biological substances, and some of the effective protection measures that can be taken, are described in 'defending against invisible killers' (LD Kozaryn, American Forces Press Service).

What will be the effects when you are exposed to one of these?
At first, nothing. It takes time for a pathogen to make a person ill. You wouldn't see, smell or taste anything exceptional. Then you might fall ill with symptoms similar to a 'flue or a cold, however these soon turn severe. You'd see a doctor, and soon doctors would realize that there is something seriously wrong with you. By then, a number of things will happen. You will receive medication, and if you're lucky you'll survive, for at an early stage antibiotics can be effective against either Anthrax and Plague. The doctor will report the case and officials will set out an alert. Then, probably, panic strikes. Can we trace down where and when the infection took place? Who else got infected? Everybody with the slightest symptoms would present to a doctor. Normal life could come to a stop. Where and when will be the next attack? How will we konw? The effect of casualties and deaths are estimated to be high (varying with the amount of agent, the way of spread, the weather, etc), but the devastating effect on the community will be immense. Exposed people further spread the infection. An epidemic, either caused naturally or by terrorism, may last for months or longer.

How likely is it that terrorists produce bioweapons?
A fermentor is easy to build and operate. Pathogenic bacteria are easy to get and to grow. The techniques to manipulate these bacteria to make them more dangerous (make them resistant to antibiotics, for instance) are harder but not impossible to obtain. Producing viruses is more complex, as we saw above, but it can not be ruled out completely that terrorists choose the hard and deadly way. In an interesting article examples are described of terroristic activities involving biological weapons in the past (Source; Scientific American). Or just check the facts from the past (Source; Scientific American). The production of biological weapons can occur unnoticed. The technical difficulty is to disperse the agent over a susceptable and innocent people. This could be done with spraying airoplaines. Once you realize what happens, you can hardly defend yourself. But at least you can be prepared: Coping with terrorism (Source: Fed. Emergency Management Agency).

A second scenario for a bioterrorist attack is the spread of a biological agent through drinking water or food that is contaminated on purpose. This can be an organism or a toxic compound that poses a danger after swallowing. Again, the effect should be severe and fast. The idea is not new: in every war there has been rumours that the enemy was contaminating water wells, and sometimes they were. See this historical overview of bioterrorism and biological warfare avant-la-lettre (Source: Fort Worth).

Cholera has been named as a candidate to contaminate water, and cholera was endemic in large parts of the world, including the US, until recently. This proves that Vibrio cholerae, the organism causing cholera, can survive in moderate climates. However, our water-cleaning facilities would soon inactivate the organism, and cholera hardly spreads from person-to-person. Having said that, naturally-occuring outbreaks of enteric diseases by contaminated water supplies are frequently occuring, which shows that the system is not perfect. Terrorists know this, too.
Botulin, the toxin produced by Clostridium botulinum, is a potent toxic agent that can be present in spoiled (canned) food

Learn more about this bacterium and its disease from this fact sheet on botulism (Source: CDC)
Use our species file on Clostridium botulinum for more on-line information.
See the Consensus statement on the recommendations for measures to be taken by medical and public health professionals if botulin is used as a biological weapon against a civilian population (JAMA 281:1735-1745, 1999)

Salmonella. back in 1997 a cult group contaminated salads with Salmonella to influence the results of county elections (Source: Emerging Infectious Diseases). In general, however, Salmonella is not regarded 'serious' enough to be used by terrorists. Contaminated food would quickly be withdrawn from the shelves, and this kind of terrorism (or threatening with it) is more likely used to blackmail companies than to do serious harm to civilians.
The possibility that bioterrorism chooses our agricultural food supply as a target can not be ignored. People would not be killed, but economy would be crippled. The economic effect of the recent Foot-and-Mouth disease in the UK could easily be equalled with a well-targeted shot of the virus into a US cow. Agricultural bioterrorism: a serious threat (Source: Iowa State Uni Faculty of Vet. Medicine)

Finally, two more interesting links:
A brief summary of toxins, including bacterial toxins (Source: Organisation for the Prohibition of Chemical Weapons)
Interview with JM Henderson on Bioterrorism, are we prepared? (Source: Action BioScience.org)

After reading this, you may not like the idea that bacteria can be used to do harm on purpose. But don't blame them.

The content of this page is copyright of the Virtual Museum of Bacteria and was written by Dr. T. M. Wassenaar (curator), with support of the Foundation for Bacteriology (Dr. M.J. Blaser, President).
Special Feature files cover various aspects of bacteria, bacteriology, and bacterial diseases and are produced with support from

The Waksman Foundation for Microbiology.

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Page last modified: 08 Mar 2005

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