There are two basic ways of using biological weapons against humanity. The first is to attack the food or water supply. This would produce hardship and the possible death from starvation of many individuals. In developed countries such as the United States, total devastation due to such an attack would likely be avoided, as there are considerable stores of food, in dispersed locations, that would mitigate against crop failure of moderate proportions.
In addition, most experts agree that the amount of biological contaminant required to overcome the effects of dilution and time in most water reservoirs makes poisoning of water supplies impractical, although not impossible.
The other way of using biological weapons against humanity is to attack individuals directly, using pathogens. Numerous known pathogens could be used, but the most effective biological weapons would creep upon the population with stealth. Naturally occurring agents that have promise as biological weapons are pathogens, which can infect and colonize a host. A pathogen causes disease, an alteration in the metabolism of a host.
In order for disease to occur, it is necessary to have a virulent pathogen, that is, one that is capable of causing disease; a susceptible host, able to be infected; and an environment that is favorable to both the host and the pathogen. When these occur together, disease occurs.
For the disease cycle to begin, it is necessary for propagules of the pathogen to come in contact with the susceptible host. Propagules include those that cause initial infections, called the primary inoculum.
As the disease cycle progresses, the host may release other propagules, considered the secondary inoculum. When only one progression of disease occurs during a prolonged span of time, the disease is termed monocyclic. When more than one cycle of disease takes place in a growing season, the disease is called polycyclic.
An example of the monocyclic disease cycle occurs with corn smut. The primary inoculum is released in the spring, as the tassel and silk of the corn appear. Infection occurs, symptoms of large black galls develop on the ears, and new inoculumis produced for the following growing season.
This kind of disease produces a single cycle during a growing season. The potential for problems depends on the amount of inoculum present at the beginning of the disease cycle. In order to use corn smut as a biological weapon, the initial amount of inoculum must be sufficient to reach all of the plants that are targeted.
This is the same general case as with anthrax. Anthrax is a disease of animals that is caused by the bacterium Bacillus anthracis. The bacterium is able to survive in nature as small spores that are able to resist extremes of climate and time.
These microscopic spores are produced at any time when environmental conditions are unfavorable for growth of the bacterium. The spores are less than 2 microns in diameter, and if they become suspended in the air, they will hang indefinitely. Such small particles are called PM 10 (particulate matter less than 10 microns in size).
These particles are of extreme importance, as they are not filtered out by common filters and must be removed by HEPA (high-efficiency particulate-arresting) filters, which can remove particles smaller than a micron. When these particles are inhaled, they cause disease of the lung tissue, which will result in destruction of the lungs and the resultant death of the host.
The reasons that Bacillus anthracis could be a biological weapon are that it is easily concealed and disseminates quickly as an invisible, airborne powder. The small particle size allows it to be inhaled, after which it lodges in the lungs and begins the process of infection. The infection begins like that of a common chest cold.
By the time the host determines that anthrax might have been contracted, the condition is normally fatal. One of the features of anthrax as a biological weapon is that it is not contagious. Spores are not produced until the host is dead, at which time the spores are not placed back into the air currents. This permits anthrax to be used against a specific target.
A plant-based example of this is the epidemic of potato late blight,which caused the Irish Potato Famine of the mid-1840’s. Most of the people living in Ireland at that time depended on their own harvests for food. During a two-year period, the climate became especially cool and damp, conditions favorable for the spread of potato late blight.
Because potatoes are planted from vegetative parts, there was genetic uniformity of the crop, which was highly susceptible. The pathogen is extremely virulent, with the capacity to destroy a single plant overnight. Total crop failure resulted in the reduction of Ireland’s population from about six million to about two million people.
About one-third of the people emigrated to other lands, and about one-third of the population died from starvation. All of this destruction could have started from a single fungal propagule that infected a plant and then spread. This fungus is still problematic world wide. However, regular sprays with fungicide reduce the risk of crop destruction.
Pathogens that occur at low levels in any given area are called endemic and may, when conditions are favorable, produce a widespread surge of disease in that area. This is called an epidemic. Epidemics that occur over wide geographic ranges, such as two or more continents, are called pandemics. The endemic potato late blight fungus caused an epidemic, and because it also spread into Europe and North America, the situation could be called a pandemic.
A similar concern is expressed with regard to the disease smallpox. Smallpox is caused by a virus that is easily passed from an infected individual to a healthy one. The smallpox virus no longer occurs in nature (is not endemic) anywhere in the world. The last reported case of smallpox in nature occurred in the late 1970’s. As a result of a concerted vaccination effort among many nations, this normally fatal disease was eradicated.
The last stores of smallpox virus are housed at the Centers for Disease Control (CDC) in Atlanta, the U.S. Army Biological Weapons Research Unit in Fort Detrick, Maryland, and the Russian Academy of Sciences in Moscow. Some people fear some of the inoculum from one of these storehouses could be transported into unconfined areas of the outside world.As such, small pox would become a very formidable biological weapon.
Smallpox is highly contagious and spreads easily from person to person. Should an infected person walk the streets of a highly populated urban area, it would be possible to infect millions of people within the span of a week or two. Within several weeks, especially in this age of global travel, the infection could spread around the world.
One method of spreading disease is through the use of vectors.Vectors are arthropods or other invertebrates that have the ability to transmit a pathogen from one host to another. The most famous vector is the mosquito, which can transmit malaria, dengue fever, West Nile virus, and many other diseases.
The corresponding vector in plants is the aphid, which can transmit a host of viruses and mycoplasmas (bacteria that lack cell walls). In order for transmission to occur, it is necessary for a vector to first come in contact with an infected host, feed upon that host, and then pass the pathogen to an uninfected host.
The most notable vector-borne disease is plague, which is passed from infected animals to humans by fleas. This disease, which was once responsible for hundreds of thousands of deaths, is now readily controlled by the use of insecticides to kill off the vector.
technology, the manipulation of the genetics of a pathogen to make it a "super pathogen" is possible. The creation of a genetic code which could be pathogenic is also possible. So-called designer weapons are those that may be envisioned by someone who feels he or she has a need to make a more destructive or more "targeted" weapon. These weapons could then be used on a specific population or area.
The creator of the designer weapon would have an advantage, as he or she would also be able to create a vaccine against the designer weapon, which could be administered to a specific group of individuals. Designer weapons, like all biological weapons, work best when there is an abundant supply of susceptible hosts and when the genetics of these hosts do not vary greatly.
There is considerable opportunity for the use of any pathogen as a biological weapon. Most pathogens can be cultured with standard laboratory equipment; however, the difficulty is in creating a system of dispersal that will effectively spread the inoculum over an area of susceptible hosts.
There are innumerable systems that could be used; these include spraying particles into the air, mailing them in an envelope, or placing them into a bomb. One of the less sophisticated methods of dissemination is the use of aircraft that are used for agricultural spraying. These aircraft could spray inoculum over large areas, with the potential of infecting large populations.