Biological agents
Overview
The threat from biological agents arises when naturally occurring microbes are weaponized—harnessed and modified to cause disease or even kill many people. Organisms can be used in their naturally occurring state, or they may be able to be modified to increase virulence and/or render the disease they cause resistant to treatment.
To determine if an outbreak may be bioterrorism, scientists will look for the following characteristics:
- A large number of cases appearing at the same time, particularly in a discrete population (e.g., people from the same town, people who attended the same event)
- A large number of cases of a rare disease or one considered a bioterrorism threat (e.g., plague, tularemia)
- More severe disease manifestation than typical for a given disease and/or an unusual route of exposure
- A disease that is unusual in a given place or is out of season (e.g., a flu outbreak in the summer in the United States)
- Multiple simultaneous outbreaks of the same disease or different diseases
- A disease that affects animals as well as humans
- Unusual disease strains or uncommon antibiotic resistance to an organism
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.
Understanding biological agents
The first step in understanding biological agents and how they affect the human body is a review of associated terminology.
Infectious Diseases
- Infectious diseases are caused by the invasion of the body by harmful microorganisms.
- Microorganisms multiply and make the person sick by attacking organs or cells in the body.
- These harmful microorganisms include viruses and bacteria, as well as certain other microscopic organisms, and are sometimes called pathogens.
- There is usually a lag time, called an incubation period, between when a person is infected and when the symptoms appear.
- People can become infected with these diseases in any number of ways, including consuming contaminated water or food, being bitten by insects or animals, or inhaling or touching the microorganisms or their spores.
Spores are produced by certain bacteria and plants. Like seeds, spores do not grow until the environment is conducive for them to do so. They are highly resistant to heat and other environmental factors. - All of the diseases discussed in this section are considered infectious diseases. Illnesses caused by chemical agents, by contrast, are not infectious diseases.
Contagious Diseases
- A contagious disease is an infectious disease that can be caught by a person who comes into contact with someone who is infected. Not all infectious diseases are contagious.
- Exposure to a contagious disease usually happens through contact with the infected person's bodily fluids or secretions, such as a sneeze.
- Depending on the disease, the level of contact required to pass on the illness could be as casual as water droplets in the air from a cough (e.g., smallpox).
- The level of contagiousness has nothing to do with how serious the resulting disease may be. For example, pneumonic plague and the common cold are both highly contagious, but pneumonic plague is obviously a much more serious disease.
- There are some infectious diseases that are not contagious at all, no matter how close the contact with an infected person (e.g., botulism, tularemia).
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