Bioterrorism

Written by Dr. T. M. Wassenaar Tuesday, 23 December 2008 16:40

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Bioterrorism is the term used for terroristic activities in which biological substances are used to cause harm to other people.  Bioterrorism is a combination of biological warfare and terrorism and due to particular events bioterrorism has received lot of attention in the first decade of this century

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 within a short time: it must have a short incubation time
  • it must be able to cause disease by inhalation (for airborne threats) or survive in water (for drinking water threats)
  • 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. Nevertheless, smallpox has been considered as a bioweapon by several countries, and repositories of the virus exist till this day. The debete whether or not to distroy these goes on.

To work with deadly viruses,  people have to protect themselves to the highest possible degree, see how virologists work at Biosafety Level 4. For this reason such deadly viral diseases are unlikely to be used as a weapon.

Bacteria are easier to produce than viruses. Therefore bacterial bioweapons 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. Only a few diseases are seriously considered as potential weapons for bioterrorists:

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'.

A second scenario for a bioterrorist attack is to spread 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. Here is an overview of  bioterrorism avant-la-lettre.

  • 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
  • Salmonella. back in 1984 a cult group contaminated salads with Salmonella to influence the results of county elections. 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.

What will be the effects when you are exposed to one of these organisms?
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 an upset stomach, 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 quite effective. 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. Exposed people may 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 (to produce bacteria at a large scale) 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. Still, the chance that you will suffer such an attack is minute, compared to the much more realistic scenario that you'll suffer your next infectious disease (serious or minor) from natural causes.

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 last 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

Finally, two more interesting links:
A brief summary of toxins, including bacterial toxins
Interview with JM Henderson on Bioterrorism, are we prepared?

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

Last Updated on Monday, 07 November 2011 21:52