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BIOLOGICAL AGENTS

The use of Pasteurella pestis, the virulent bacterium which causes the bubonic plague, by the Tartars who in 1346 besieged Ferdosiya (Kaffa), an important port on the Black Sea, is the first recorded instance of biological warfare. Corpses of people who had died due to the plague were launched with catapults beyond the walls of the besieged city and the plague spread so rapidly within the city's population, so much so that they surrendered after having bravely withstood three years of besiege. But all Europe paid the price for this Tartars's victory. In 1347 some ships coming from Kaffa docked in Sicilian harbors. Within a few days all sailors died for the plague while rats from those ships were diffusing the Black Death, or bubonic plague, inland. By winter 1948 the plague had already reached Paris and, by 1350, 25 million people, at the time one third of the whole European population, had been killed by the plague while by the end of the same century close to 70 percent of the entire European population had died, killed by the Black Death.
Nowadays biological agents and toxins to be eventually employed in warfare, are consistently produced and stored in the arsenals of diverse countries. Aerosols which are suspensions of fine powders or liquids entirely contaminated by, or entirely composed by, disease carrying organisms or toxins may be disseminated through tiny escape nozzles fitted along the wings of military aircraft, rather similar to civilian crop-spraying aircraft. Alternatively , the aerosol can be incorporated in a container which, when parachuted into a target area, automatically opens jet nozzles to release it contents on the way down to the surface. Other disseminating methods, involving the use of bombs, shells and rocket missiles, eject aerosol cans and canisters all over a target area by small premature explosions. Once released into the atmosphere aerosol particles are subject to certain physical and environmental factors. Initially, atmospheric conditions tend to shorten the life of the organisms and hence curtail their ability to cause extensive infection. Under stable atmospheric conditions a particle between 1 and 5 microns (1 micron is equal to 1/1000 millimeter) falls at the rate of 1.5 meters per hour. Actually this pattern is disturbed by the wind and carries the aerosol back and forth across the target area, while high winds tend to disperse the aerosol. Humidity and temperature are other important factors affecting the life of aerosol organisms, i.e., particles may lose much of their water content by evaporation. This leads to a higher concentration of salts around the organism which draw more moisture from the microbial cells, further dehydrating them. When the air humidity is high, minimum dehydration occurs, while the reverse is true, i.e., when the humidity is low maximum dehydration occurs. Some organisms survive drying, others do not. Since the sun radiates ultraviolet light which kills most bacteria in a few minutes, biological weapons may be mostly disseminated by night. As well, atmospheric pollutant gases, such as nitrous dioxide, sulfur dioxide, ozone and carbon monoxide have been found to affect the survival of many pathogens. And, finally, pathogens require time to invade a body and multiply enough to overcome the body's defenses, i.e., an incubation period with may vary from hours to months.