Throughout history, infectious diseases contracted naturally have had a significant impact on military operations. The intentional dissemination of disease adds a new dimension to threats that are posed by infectious and toxic agents traditionally transmitted only by natural routes. Biological agents reportedly have been employed to a limited extent during recent military conflicts (for example, dispersion of plague bacilli during World War II and use of trichothecene mycotoxins ("yellow rain" in South East Asia); however, their use actually dates from antiquity.
The qualitative and quantitative impact of biological warfare, or the threat of such warfare, on military forces and urban communities has changed markedly in the past 20 years. Improved production techniques have resulted in more virulent strains of organisms and the genetic modification of non-pathogenic organisms to pathogenic strains with virulent characteristics. The implications of genetic engineering for chemical and biological warfare are far-reaching. Genetic engineering provides the potential for improved virulence by the incorporation of genes (i.e., specific strands of DNA) permitting increased production of a pathogen or toxin. Thus, as much as 100 times more pathogen or toxin could be produced per cell than that which could be produced by naturally occurring strains. Cells that normally do not produce toxins may be altered to produce toxins for biological weapon development. Conversely, known pathogens or toxins may be genetically inactivated for vaccine countermeasure development. Cells can also be modified to produce antibodies directly for passive immunization against specific infectious agents. As with the human immune system, many current biowarfare detection kits depend on antibodies reacting with the antigenic surface coatings of pathogenic bacteria or viruses. Thus, modified non-pathogens can be used to mask the agent from the immune-based detector and, potentially, from the human immune system itself to increase the agent's effectiveness.
General robustness or survivability of a pathogen under the environmental stresses of temperature, ultraviolet (UV) radiation, and desiccation (drying) can also be genetically improved to promote stability during dissemination; nutrient additives are used to enhance survival of selected biological agents in aerosols. Controlled persistence of a pathogen to permit survivability under specified environmental conditions may eventually be possible. The potential also exists for the development of so-called "conditional suicide genes," which could program an organism to die off following a predetermined number of replications in the environment. Thus, an affected area may be safely reoccupied after a predetermined period of time.
Intrinsic features of biological agents which influence their potential for use as weapons include: infectivity; virulence; toxicity; pathogenicity; incubation period; transmissibility; lethality; and stability. Unique to many of these agents, and distinctive from their chemical counterparts, is the ability to multiply in the body over time and actually increase their effect.
II. Biological Threats Stemming From Human Activity
Civilian R&D such as research on dangerous pathogens; the field testing of genetically organisms; the marketing of products that eventually cause negative side effects; and/or the accidental spillage of contaminated materials into the environment.
1. R&D in military or civilian laboratories for the purpose of producing a biological weapon. Two components - pathogen + delivery system
a. Low Tech System - the pathogen [usually an easily obtained pathogen or its bio toxin]; and a low tech delivery system [i.e. sealed glass container].
b. High Tech System - any naturally existing or man-made pathogen [modified in virulence and ability to survive adverse conditions]; and a high tech delivery system [i.e. missile].
c. Delivery via Living System - Human, Animal or Plants deliberately infected for the purpose of spreading disease.
2. Commercial Contamination
a. Deliberate infection of, or failure to cleanse, a food, hygiene, medical, etc. product; and the eventual dispersement of that infected product to unknowing individuals.
b. Deliberate violation of a public health law knowing full well that the act may cause the spread of disease [i.e. illegal dumping of untreated materials known to contain biohazards; the illegal disposing of biohazard material such as used syringes; etc.].
III. Zoonotic Etiology
This category may be natural or the result of human activity. It is recognized that the reservoirs of several emerging infectious diseases are animals. Among these are Sin Nombre (a hantavirus), and hemorrhagic fevers such as Marburg, Ebola and Lassa. Others are zoonoses -- diseases that affect both animals and humans. Rabies is probably the best known zoonosis. Recently emerging zoonotic diseases are (1)West Nile virus, which has now been discovered in the United States and has killed both wild birds and caused disease in humans; (2) Nipah virus, which emerged in Malayasia killings pigs and humans; and (3) in Australia, Hendra virus, which can kill horses and humans.
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