Plagues and Peoples

For most of human history, the treatment of disease was left to incomplete scientific knowledge handed down from medieval medical philosophers like Galen and Avicenna, and to direct observation and inherited knowledge passed along via folkways. The results were as often harmful as they were helpful, yet with the global homogeneity of disease, and its increasingly endemic nature, more disease presented within living subjects to be observed and compared. With the rise of a professional medical class, and of the university learning structure, doctors began to use sounder medical practices. Paracelsus (1493-1541) was among the first medical observers to reject older, unscientific methods of study and treatment. However, expert medical knowledge did not reach meaningful demographic impact until the 18th century.

The demographic results of the overall trend towards the taming of disease was first felt in China. In the century after the peaceful and orderly Manchu Dynasty was instituted in 1683, the Chinese population doubled, “rising from 150 million in 1700 to about 313 million in 1794” (247). China had a large landmass in which to expand and was an early adopter to the modern practice of inoculation. “China’s circumstances, in other words, gave full scope to the new possibilities inherent in the changed disease regime,” writes McNeill (250). To a lesser degree only Russia and the Americas followed the same demographic path, though neither population spectacularly increased due to lack of access to modern medical infrastructure. Ireland posed a special case in this regard, as their dependence on potato production substantially increased their number from 1652 until the famines of the 1840s.

Britain, on the other hand, would not see increased demographics for a century or more after the Chinese, when their extensive trade networks and innovations in tillage increased the variety and efficiency of their food supply. The increase of cattle served to decrease malaria, as the mosquitos known to carry the disease preferred the cattle who were poor carriers of malaria. Cattle stock also increased the intake of protein in the average English diet, which served to bolster the creation of antibodies against disease.

Though its use was effective, inoculation against smallpox and other diseases—the deliberate application of a less-severe form of a disease in order to build antibodies against its more extreme forms—took a long time towards mass adoption in Europe and the Americas. In England, it was readily adopted by the royal family, but only accepted by significant majorities after safer methods of vaccination had been achieved by using cowpox. Resistance was greatest in the cities, where mass populations tended to make disease endemic through repeated contact. It was in the countryside and in the remote American colonies where vaccination was more quickly adopted, as the disease proved deadlier to people outside of the cities.

Vaccines were slower to take in Continental Europe, not becoming popular until after 1800 or so. By contrast, the folk habit of inoculation against disease in Turkey, Arabia, North Africa, Persia, and India was centuries old and widely practiced before it became professionalized. In either case, after 1800, the rate of vaccinations increased severalfold, becoming common practice. This increase in health symbiotically led to a furthering of faith in enlightenment ideals, culture, and politics.

Nevertheless, other factors contributed to a balancing diminishment of human health. Conditions suffered by industrial workers seriously diminished life and health, while the Napoleonic wars continued a trend in macroparasitism. Owing to a fungus brought over from Peru, the Irish potato famine killed millions, and halted the rise in Irish population. Finally, increased urbanization led to repeated incidences of older disease patterns.

Among the greatest of these threats was the cholera outbreak in the early 1800s. Cholera killed quickly—and to horrible effect—radically dehydrating its victims. Records indicate that its first European spread came from Calcutta in 1817, cutting through English soldiers. Sea routes rapidly spread it around the world, such that outbreaks became common in the 1830s. This accelerated the debate between those who held to the modern germ theory of disease versus the “miasmists” who taught that cholera was produced by the miasma produced by the breakdown of rotting things. For a generation, the miasmic theorists won, continuing the pain of infection. Not until the invention of increasingly powerful microscopes in the late 1800s did germ theory begin to be taken seriously enough to be acted upon.

Nevertheless, a social trend towards greater sanitation ameliorated the effects of the disease. Cholera was identified as spreading through contaminated water, and political reform efforts in Europe and America emphasized “sanitation, housing, health services and water supply” (273). Cleanliness and “spit and polish” was soon adapted by, and became intrinsic to, modern military practice. Cholera prompted the establishment of an English Central Board of Health in 1848, which in turn began the process of modernizing and extending sewer systems throughout the country. Other countries soon followed, and those without the infrastructure for modern sewage nonetheless learned simple preventative measures, such as testing and boiling of water, which made urban life much safer by 1900. These changes precipitated the modern turn toward urbanization, with more and more people leaving the country to live in the city, which redefined work, culture, and demography.

Cholera also served to coordinate the efforts of doctors, policymakers and scientists. By 1893, a vaccine for cholera was developed, and at the dawn of the 20th century, countries across the world mandated vaccinations. This coordination served to isolate and treat other diseases such as typhus (for which a vaccine was developed by 1896) and diphtheria (which was diminished through the pasteurization of milk). Quinine was discovered as an imperfect palliative for the symptoms of malaria, and that disease, as well as yellow fever, were effectively controlled by the reduction of mosquito populations and by 20th century vaccines. As in the 19th century, the military arm of several countries played a role in establishing vaccine and sanitary regimens. The complete mobilization of the industrialized economies during the First and especially the Second World War led to greater understanding of sanitary and dietary needs of masses of people The World Health Organization was founded in 1948 to advance new knowledge in these burgeoning fields.

The last great worldwide outbreak of disease for which the world was not prepared was the great Influenza outbreak in the aftermath of the First World War, killing 20 million or more worldwide. Though vaccines for its various strains become available quickly, reducing its toll of death, the nature of influenza virus is such that it mutates with wild rapidity, requiring new vaccines on a rotating basis. Its future effects, as of the publication of McNeill’s 1976 book, were unknown.