Every 3 seconds or so, a human being inhales and exhales about a pint of air. Each cycle draws in oxygen to fuel the body and releases carbon dioxide, the gaseous waste product. The inhaled air commonly carries with it floating incidentals such as dust, bacteria, and other microscopic particles. If a particle is larger than 5 microns, it is likely to be blocked from reaching deep into the lungs by the respiratory tract’s mucus and filtration hairs. If smaller than 1 micron, a particle is too small to be retained and is blown out during exhalation.
Anthrax: From a medical detective
Anthrax is a serious infectious disease caused by gram-positive, rod-shaped bacteria known as Bacillus anthracis. An anthrax spore may be 1 micron wide and 2 or 3 microns long, just the right size to reach deep into the respiratory pathway. A spore is so tiny that a cluster of thousands, which would be enough to kill someone, is scarcely visible to the naked eye. A thousand spores side by side would barely reach across the thin edge of a dime. Once inhaled, the spores are drawn into the bronchial tree where they travel through numerous branches deep in the lungs. Near the tips of the branches are microscopic sacs called alveoli. It is in these sacs that inhaled oxygen is exchanged with carbon dioxide.
Stationed among the alveoli are armies of defender cells called macrophages. These cells sense foreign micro-invaders and engulf them. A pulmonary macrophage normally destroys its inhaled captive and taxis it to the lymph nodes in the mediastinum, the area between the lungs. But in the case of anthrax, spores may transform into active, germinating organisms before the macrophage can affect them. The bacteria then can reproduce and release toxin that destroys the macrophage. Thus, in a perverse turnabout, the anthrax bacteria, like soldiers in the Trojan horse, can burst out of their encirclement, into the lymph and blood systems.
An Infected person
An infected person at first is unaware that a gruesome cascade is underway. Although the onslaught is relentless, symptoms do not appear immediately. Fluids that have begun to accumulate in the mediastinum gradually pry the lungs apart. Breathing becomes increasingly difficult, and after a few days a person feels as if his head is being held underwater, permitted to bob up for a quick gulp of air and then pushed under again. The agony works its way through the body. Nausea gives way to violent, bloody vomiting. Joints are so inflamed that flexing an arm or leg becomes an act of torment. Bloody fluids squeeze between the brain and skull, and the victim’s face may balloon out beyond recognition. The tightening vice around the brain causes excruciating pain and delirium. Survival depends on being provided appropriate antibiotics before the bacteria have released so much toxin that the body cannot recover. If inhalation anthrax is not treated in time, almost all victims suffer a tortured death. One organ after another is decimated—the lungs, the kidneys, the heart— until life is sucked away.
It is because of such ghastly effects that anthrax and other biological agents have been prohibited as weapons by international agreement. The treaty that bans their development or possession by nations, the 1972 Biological Weapons Convention, uniquely describes their use as “repugnant to the conscience of mankind.” Yet despite this widely accepted moral precept, a germ weapon is seen by some not as a shameful blight but as a preferred instrument of terror.
From: The Anthrax Letters: A Medical Detective Story by Leonard A. Cole
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