Free The Demon in the Freezer by Richard Preston

midgepoxes torment midges. Grasshoppers are known to suffer from at least six different grasshopperpoxes. If a plague of African locusts breaks out with locustpox, the plague is hit with a plague, and is in deep trouble. Poxviruses keep herds and swarms of living things in check, preventing them from growing too large and overwhelming their habitats. Viruses are an essential part of nature. If all the viruses on the planet were to disappear, a global catastrophe would ensue, and the natural ecosystems of the earth would collapse in a spectacular crash under burgeoning populations of insects. Viruses are nature’s crowd control, and a poxvirus can thin a crowd in a hurry. For most of human history, the human species consisted of small, scattered groups of hunter-gatherers. The human species did not collect in crowds, and so it was almost beneath the notice of a pox.
    With the growth of agriculture, the human population of the earth swelled and became more tightly packed. Villages grew into towns, and towns grew into cities, and people began to live in crowds in river valleys where the land was fertile. At that point, the human species became an accident with a poxvirus waiting to happen.
    Epidemiologists have done some mathematics on the spread of smallpox, and they’ve found that the virus needs a population of around two hundred thousand people living within fourteen days of travel from one another or the virus can’t keep its life cycle going, and it dies out. Those conditions did not occur until the appearance of settled agricultural areas and cities, about seven thousand years ago. Smallpox could be described as the first urban virus.
    The virus’s genes suggest that it was once a rodent virus. Smallpox might once have lived in a rodent that multiplied in storage bins of grain. Perhaps, perhaps not. Smallpox might be a former pox of mice, or it might be a ratpox that moved on. Maybe, maybe not. There is, however, a strong suspicion that smallpox made its trans-species jump into humans in one of the early agricultural river valleys—perhaps in the valley of the Nile, or along the Tigris and Euphrates in Mesopotamia, or in the Indus River valley, or possibly along the rivers in China. By 400 B.C., the population of China had grown to twenty-five million people, which was probably the largest and densest collection of people at that time, and they were crowded along the Yellow River and the Yangtze. Down by the river somewhere, the pox found its human lover.
    The mummy of the Pharaoh Ramses V, who died suddenly as a young man in 1157 B.C., lies inside a glass case in the Cairo Museum. His body is speckled with yellow blisters on his face, forearms, and scrotum. It looks like a centrifugal rash. Pox experts would very much like to look at the soles of the pharaoh’s feet and the palms of his hands, to see if there are any blisters on them, for that would be a sharp diagnostic sign of smallpox. But the pharaoh’s feet are wrapped in cloth, and his hands are crossed over his chest, palms downward, and the authorities at the Cairo Museum will not allow anyone to move them. Pox experts would also like to clip out a bit of the pharaoh’s skin and test it for the DNA of smallpox virus, but so far that has not been allowed either.
    Another possibility for the point of contact between humans and variola is Southeast Asia around 1000 B.C. Crowded city-states were developing there. Or the original host of smallpox may have been an African squirrel that lived in a crescent of green forests that are thought to have once existed along the southern reaches of the Nile River. The climate dried out, the forests disappeared or were cut down by people, the country turned into grasslands, and the squirrel became extinct. Variola moved on.
    It is possible that variola caused the plague of Athens in 430 B.C., which killed Pericles and dealt the city a devastating blow during the opening years of the Peloponnesian War with Sparta. Variola