Pox_ An American History - Michael Willrich [13]
The bond between variola and humans is not merely a virological curiosity. It is a fact of epidemiological and even world-historical significance. It is perhaps the essential fact about a virus that killed at least three hundred million people during the twentieth century alone—more than all of the century’s wars. There is no animal reservoir or vector for smallpox. It cannot be transmitted by mosquitoes (as with malaria) or lice (typhus) or rat fleas (bubonic plague) or domestic animals (anthrax). Nor, for that matter, can smallpox infect people through their sewage-tainted water supplies (as does cholera) or contaminated food (typhoid fever). Smallpox can spread only from one person to another, normally through face-to-face contact.22
Smallpox is, as George W. Stoner observed in his Handbook for the Ship’s Medicine Chest (1900), a “self-limited disease.” An attack followed a distinctive clinical course for which there could be but two outcomes: smallpox either killed its victim or left the survivor immune for life. Although particles of the virus could persist for long periods in scabs on the bodies of the dead, variola did not remain in a living body after convalescence. There was no chronic recurrence, as in many herpes viruses. Smallpox survivors did not become symptomatic and infectious time and time again. They could never again get or spread the disease. This, rather than an appreciation for the poetry of the situation, was why Dr. Long hired Reverend Smoot to drive the pesthouse wagon.23
Human beings appear to be universally susceptible to the variola virus. Unless they have been made immune by a previous infection with variola or another orthopoxvirus—such as cowpox or vaccinia, the principal viruses used in vaccination—they will almost certainly develop smallpox if the virus particles enter their respiratory tracts.
Together these facts about the variola virus begin to explain the epidemiology of smallpox—its behavior in human communities. When the virus entered a population, smallpox tended to be passed around until most people had been infected. In small, relatively isolated populations, such as most towns of colonial North America, the virus would soon die out. The virus particles did not normally survive for long outside the human body, and when the ranks of vulnerable humans were exhausted, variola had no place to replicate. For smallpox to become endemic in a given population (prevalent for a long period at a relatively low level), there had to be a steady influx of susceptible bodies, whether through significant levels of in-migration or by natural reproduction. This is why in societies where endemic smallpox existed, such as European or English cities in the eighteenth century, small-pox was known as a disease of children. Most children born in London had smallpox before their seventh birthdays; the disease was a rite of passage. In English towns, nine out of ten fatal smallpox cases occurred in children under five. It was endemic smallpox that the nineteenth-century British historian Lord Thomas Macaulay famously called “the most terrible of all the ministers of death.” “The smallpox was always present,” he wrote, “filling the churchyard with corpses, tormenting with constant fear all whom it had not yet stricken, leaving on those whose lives it spared the hideous traces of its power, turning the babe into a changeling at which the mother shuddered, and making the eyes and cheeks of the betrothed maiden objects of horror to the lover.”24
Of course, the “speckled monster” earned its worldwide infamy by its