Biological agents
By U.S. Department of Health and Human Services
Posted 3/29/06
Page 2 of 5
Toxins
- Toxins are the poisonous, usually protein-based, substances produced by microorganisms (bacteria, mold, virus) in certain infectious diseases.
- Microorganisms use these toxins as the specific weapons for attacking organs or cells in the body.
- Antitoxins are medications that attempt to neutralize a toxin without necessarily killing the bacteria, mold, or virus that is producing the toxin.
- Many different types of antitoxins exist, because a specific antitoxin will usually only fight a particular kind of toxin.
- Although toxins are usually classified as being biologically produced, common language often refers to the poisons created by nonliving chemical agents as chemical toxins.
- Although some of these characteristics may be true of a naturally occurring outbreak, they will generally signal that the outbreak needs to be closely scrutinized.
Bacteria and Viruses
Both bacteria and viruses can cause infectious diseases.
Bacteria:
- Bacteria are one-celled microorganisms that are capable of multiplying.
- Not all bacteria are harmful (e.g., bacteria turn milk into cheese).
- Antibiotics are medications that can be used to kill harmful bacteria.
- Some bacteria can develop resistance to antibiotics, making the medications less effective.
- Hospitals will typically have supplies of antibiotics known to be effective against most Category A and B bacterial agents.
Viruses:
- Viruses are simpler than bacteria, often made up merely of a bit of deoxyribonucleic acid (DNA) or ribonucleic acid (RNA) that is surrounded by a protective coat of protein.
- Viruses are parasitic in nature and unable to multiply without host cells—cells within a person's body that the viruses invade and use to multiply.
- Antibiotics are not effective against viruses.
- Some antiviral medications do exist, but many that might help against Category A agents are still in clinical trials. Consult HHS's National Institutes of Health's National Institute for Allergy and Infectious Diseases' (NIAID) Web site for ongoing research in this area.
Delivery of biological agents
The ability to successfully deliver a biological attack depends on:
- The type of agent or organism
- The method of dissemination
- The weather (e.g., wind speed, humidity, time of day, precipitation, temperature):
Wind speed affects how widely an agent can be spread
Humidity can cause decomposition of an agent
Precipitation can cause clumping, making fine particles more difficult to inhale
Routes of Entry
Biological agents can enter the body through:
- Absorption
- Inhalation
- Ingestion
- Injection
Delivery Methods
Biological weapons can be prepared for delivery as a weapon in wet or dry form:
- In dry form, agents are more stable and refinement is easier.
- In liquid form, agents are less stable, require refrigeration, and are difficult to refine to small particle sizes.
Biological weapons can be delivered by:
- Wet or dry aerosol sprayers
- Explosive devices
- Transmission through insects, animals, or humans
- Introduction into food, water, or even medications
- In or on objects, in some cases (e.g., anthrax in envelopes)
Effectiveness of Release
The effectiveness of a biological release depends on:
- The particle size and its potency (for example, in an aerosol release, the size must be between 1 and 5 microns to be inhaled and cause illness). (Note: 1 micron is one millionth of a meter. A strand of hair ranges between 20 and 200 microns in width.)
- How well the agent survives in the environment
- Weather conditions
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