Smallpox virus interacts with the victims' immune systems in different ways, and so it triggers different forms of disease in the human body. There is a mild type of smallpox called a varioloid rash. There is classical ordinary smallpox, which comes in two basic forms: the discrete type and the confluent type. In discrete ordinary smallpox, the pustules stand out in the skin as separate blisters, and the patient has a better chance of survival. In confluent-type ordinary smallpox, which Los had, the blisters merge into sheets, and it is typically fatal. Finally, there is haemorrhagic smallpox, in which bleeding occurs in the skin. Haemorrhagic smallpox is virtually one hundred per cent fatal. The most extreme type is flat haemorrhagic smallpox, in which the skin does not blister but remains smooth. It darkens until it can look charred, and it can slip off the body in sheets. Doctors in the old days used to call it black pox. Haemorrhagic smallpox seems to occur in about three to twenty-five per cent of the fatal cases, depending on how hot or virulent the strain of smallpox is. For some reason black pox is more common in teenagers.
The rims of Barbara Birke's eyelides became wet with blood, while the whites of her eyes turned ruby red and swelled out in rings around the corneas. Dr William Osler, in a study of black-pox cases he saw at the Montreal General Hospital in 1875, noted that 'the corneas appear sunk in dark red pits, giving to the patient a frightful appearance'. The blood in the eyes of a smallpox patient deteriorates over time, and if the patient lives long enough the whites of the eyes will turn solid black.
With flat haemorrhagic smallpox, the immune system goes into shock and cannot produce pus, while the virus amplifies with incredible speed and appears to sweep through the major organs of the body. Barbara Birke went into a condition known as disseminated intravascular coagulation (DIC), in which the blood begins to clot inside small vessels that leak blood at the same time. As the girl went into DIC, the membranes inside her mouth disintegrated. (50-51)
As the end approaches, the smallpox victim can remain conscious, in a kind of frozen awareness - 'a peculiar state of apprehension and mental alertness that were said to be unlike the manifestations of any other disease' (52)
The IL-4 gene holds the recipe for a common immune-system compound called interleukin-4, a cytokine that in the right amounts normally helps a person or a mouse fight off an infection by stimulating the production of antibodies. If the gene for IL-4 is added to a poxvirus, it will cause the virus to make IL-4. It starts signalling the immune system of the host, which becomes confused and starts making more antibodies. But, paradoxically, if too many antibodies are made, another type of immunity goes down -- cellular immunity. Cellular immunity is provided by numerous kinds of white blood cells. When a person dies of AIDS, it is because a key part of his or her cellular immunity (the population of CD4 cells) has been destroyed by HIV infection. The engineered mousepox seems to create a kind of instant AIDS-like immune suppression in a mouse right at the moment when the mouse needs this type of immunity the most to fight off an exploding pox infection. An engineered smallpox that triggered an AIDS-like immune suppression in people would be no joke (280-281)
(London: Headline, 2003)
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