Pathogenesis: A History of the World in Eight Plagues

by Jonathan Kennedy

A plethora of recent discoveries point to the fact that Homo sapiens weren’t, in fact, smarter than other species of human.

he was blind in one eye as a result of a crushing blow to his head at a young age; his right arm was withered, and had possibly been amputated; he had fractured a metatarsal on his right foot, which had healed; and he was profoundly deaf.[40] This find is astonishing because it suggests that the band of Neanderthals living in Shanidar were willing and able to look after a very vulnerable member of their community. Such expressions of compassion are widely understood to be one of the key characteristics of a civilized society; indeed, for the anthropologist Margaret Mead, human civilization began when we started to care for the weak and sick.[41]

This process has been called the “poison-antidote model” of adaptive introgression: Neanderthals gave Homo sapiens a “poison” by exposing them to a novel pathogen, but also the “antidote” in the form of introgressed gene variants that confer resistance to the pathogen.[61] As a result, many of the Neanderthal gene variants that remain in our genome relate specifically to our immune response.[62]

Rome itself was served by eleven aqueducts that transported over half a million cubic meters of water into the heart of the imperial capital every day—that is, about 500 liters per person.[18] The aqueducts provided water for drinking, bathing and public fountains. Even now, the water in the Trevi Fountain is supplied by an aqueduct dating from the first century CE. The water supply made living in a city the size of Rome possible—a point Pliny the Elder understood when he wrote: “there is nothing to be found more worthy of our admiration throughout the whole universe.”

Germs Are Deadlier than Germans

a Franciscan monk in Kilkenny, Ireland, who died in the plague, left blank pages in his chronicle and a message in case “any child of Adam may escape this pestilence and continue the work thus commenced.”[17] Below this, someone added a postscript dated 1349: “it seems that the author died here.”

The Italian city-states were the first communities to take action to protect themselves from the plague. Starting in the 1370s, all ships wanting to enter Venice had to wait on the nearby island of San Lazzaro until the health magistrates granted the crew permission to disembark. Over time, the waiting period became standardized at forty days—the word quarantine is derived from quaranta, the Italian for forty.

But the superiority of the Old World has been overstated. There weren’t big disparities in living standards between late-medieval Spain and the pre-Columbus Americas. In a letter to the king, Charles V, Cortés described with amazement how Tenochtitlan’s buildings, pottery, jewelry, clothes, shoes, food, markets and barber shops were either similar to or of better quality than those in Spain.

That same year, an English trading company—the Popham Colony—tried to set up a base in what is now southern Maine but abandoned the project after fourteen months, in large part because of opposition from numerous well-armed Native Americans. The French attempted to found a settlement near Chatham, Cape Cod around the same time, but it failed for similar reasons. Then, improbably, a small, ragtag group of English Separatists who had been exiled in Leiden landed in late 1620 and managed to start the first permanent settlement in New England. Why did the Pilgrims succeed where others failed? It wasn’t because they were better prepared or more numerous. Rather, between 1616 and 1619 a savage epidemic had swept through the Massachusetts Bay area, most probably brought by European fishermen or traders who operated there. Some scholars believe it was smallpox, others viral hepatitis. Either way, it is estimated to have killed as much as 90 percent of the population.[56] If modern-day Americans want to be historically accurate, then their gratitude at Thanksgiving should be directed to the Old World pathogens that made the settlement of Plymouth Colony possible.

Oliver Cromwell, who headed an austere Protestant dictatorship after the execution of Charles I in 1649, came down with malaria but stubbornly refused to take a medicine that was so closely associated with papists.[85] He died shortly afterward. Charles II, who replaced Cromwell, had no such qualms and survived a bout of what was then referred to as the ague.

Between 1550 and 1650, 650,000 Africans were trafficked to Spain and Portugal’s American colonies—more than twice the number of Europeans who crossed the Atlantic in that period.[19]

“Thus,” wrote the historian John McNeill, “Great Britain was born, with the assistance of fevers from Panama.” Over 300 years later, the union is a major political issue and pro-independence parties currently hold a majority in the Scottish parliament. New Edinburgh was a particularly spectacular example of the damage that infectious diseases wrought among white colonial would-be settlers in the American tropics. But the colonies that lasted did so because plantation owners quickly learned that trafficked West Africans provided a much more reliable source of labor than Europeans.

The British economic miracle didn’t occur simply because of its industrialists’ entrepreneurial spirit. The state intervened to make sure that the odds were stacked in the favor of the domestic economy: for example, British companies could export cotton cloth with almost no tariffs, but their producers were charged duties of up to 85 percent to import textiles into the UK.[5]

Life expectancy for factory laborers was seventeen in Manchester and fifteen in Liverpool.[21] Death rates were so high among the urban working classes that the population was only able to sustain itself because of the continual inflow of people from the surrounding countryside, and increasingly from Ireland. As northern towns and cities were the epicenter of the Industrial Revolution, this is clear evidence that economic growth and increasing real wages did not automatically lead to improvements in health via the invisible hand of the market. Instead, the rapidly growing urban population in the late nineteenth century was experiencing what Simon Szreter terms the “4 Ds”: disruption, deprivation, disease and death.

Even minors weren’t spared. The content of the Factory Act of 1833 gives you a taste of the working conditions at the time. Most strikingly, it limited children between the ages of nine and twelve to forty-eight hours of work a week. Even these restrictions were contested by economic liberals, who viewed child labor laws as unjustified state intervention in the functioning of the free market.[23]

Chamberlain’s strategy proved very popular among the newly enfranchised working classes, who had the most to gain but didn’t have to pay taxes. As a successful businessman, Chamberlain’s views on the matter were respected by many influential people who would otherwise have been skeptical. While Chamberlain and his colleagues were in large part driven by altruism—which set them apart from Chadwick and his ilk—the economic benefits of their strategy weren’t lost on them either. They understood that ignoring health was counterproductive. A sickly working class was not just bad for the urban poor, who got ill and died; it was also bad for wealthy business owners, who relied on them to labor in their factories.

In the UK, the national government did play a role in these developments, through providing loans and sharing best practice. But it was not directly involved in efforts to improve the lives of the urban working classes in the last three decades of the nineteenth century.[70] This changed when the New Liberal government that included Winston Churchill and David Lloyd George won a landslide victory in the 1906 general election. They ushered in a new era of centrally organized and funded state activism. Within the space of a few years, the government had established initiatives including old age pensions, labor exchanges, free school meals and workers’ national insurance against sickness and unemployment.[71]

Despite the remarkable advances in public health, human existence is still plagued by disease and death.

And yet, despite the fact that there is a cheap and reasonably effective vaccine available—it costs a couple of dollars per dose—and TB can be treated with a course of antibiotics, it is still the most deadly infectious disease in the world. It kills about 1.2 million people a year, almost all of whom live in lower- and middle-income countries.

Vaccinations against the plague resulted in an 80 percent drop in cases in the first year alone. TB cases fell by 80 percent in a decade due to increased use of the BCG vaccine.

People were now required to purchase health insurance, but 90 percent of the rural population couldn’t afford to pay; for the uninsured, one visit to the doctor could easily cost a poor family a third of their annual income.[32] Barefoot doctors’ work was abandoned because individuals weren’t willing to pay for preventative public health programs. Patients even had to pay doctors for vaccinations and, as a result, immunization rates fell to under 50 percent.[33] Infectious diseases surged, including measles, polio, TB and schistosomiasis.

My intention here isn’t to advocate communism. Rather it’s to demonstrate that, just as the state was crucial in defeating infectious diseases in late-nineteenth-century Britain, it was also vitally important in China’s escape from the poverty trap in the late twentieth century. Yet we must not overlook the massive downsides to the Chinese model of development. The improvements in health and wealth have been achieved despite an Orwellian disregard for individual freedom and human rights—from the Great Leap Forward to the present-day treatment of the Uighurs, and of course the response to Covid-19. Notwithstanding, it was the iron fist of the totalitarian state that pulled China out of the poverty trap rather than the invisible hand of the market.

Recipient countries were often required to cap the public-sector wage bill, resulting in the emigration of large numbers of doctors and nurses to high-income countries. In the 1980s, the number of doctors in Ghana fell by half, and only one-sixth of Senegal’s nurses remained, compared to the start of the decade.[46] Structural adjustment programs frequently introduced user fees for health care that mimicked the U.S. model. As a result, the poor were unable to access even the most basic care. For example, when the World Bank forced Kenya to impose a charge of thirty-three cents to see a doctor, patient visits fell by half.[47] (The number of patients almost doubled when the fee was suspended.) And it has been shown that structural adjustment caused an increase in some infectious diseases, including TB.[48] From 1980 to 2000, life expectancy in sub-Saharan Africa barely increased at all, remaining stuck at around fifty years.

If I jump on a train at Euston station that is heading north, I can be in the seaside resort of Blackpool in less than three hours. Male life expectancy in the town is a full twenty-seven years lower than in Kensington and Chelsea—the same as the difference between the UK or the U.S. and the unhealthiest countries in sub-Saharan Africa. Prior to the Covid-19 pandemic, the disparities in life expectancy within the UK were not explained by the differential impact of infectious diseases, as they killed far too few people to make a mark. Rather, inequalities in health outcomes were the result of disparities in premature deaths from non-communicable diseases, most notably cardiovascular disease, cancers and diabetes. While such illnesses obviously aren’t transmitted from one person to another by pathogens, their distribution is not random. Just as the urban working classes in Victorian slums were more likely to be affected by cholera or TB, these modern “plagues” disproportionately impact the poor—hence the inequalities in health outcomes between places like Kensington and Chelsea on the one hand and Blackpool on the other. According to the Office for National Statistics, men and women in the most deprived areas of England were, respectively, 4.5 times and 3.9 times more likely to die young from preventable causes than those in the wealthiest areas.[52] Health is so closely linked to wealth and social status that Michael Marmot, the influential British epidemiologist, has liken...

The local doctors have coined the phrase “Shit Life Syndrome” to refer to the common denominator for most of the maladies they see: destitution and hopelessness.[57] The suffering we see in Blackpool is a consequence of deindustrialization—or what some economists have called the “deindustrial revolution.”[58] Work in factories, as well as mines and docks, was often hard and dirty, but it gave people a sense of security, identity and community. Over the past fifty years, most of these jobs disappeared, lost to machines and the flight of manufacturing to countries like China, where production costs are cheaper. In the 1970s, almost 8 million people were employed in the manufacturing sector in the UK; now the figure is 2.5 million, even though the population has grown by a fifth.[59]

There is, of course, one major difference between the UK and the U.S.: their health care systems. Despite a decade of Thatcherism in the 1980s and another decade of austerity in the 2010s, Britain’s National Health Service more or less survived as a system funded by national taxation that provides free health care to anyone who needs it. This contrasts starkly with the brutally inefficient privatized system in the U.S. The United States spends more on health care than any other country—almost $11,000 per person every year, compared to $4,300 in the UK, for example.[65] And yet health coverage is patchy. Those Americans who can afford to pay benefit from the best health care anywhere in the world. Yet tens of thousands of people die prematurely every year because they are unable to access health care.[66] More than 30 million are uninsured, and even people with insurance face such high costs that a quarter of the population have reported delaying seeking medical treatment and half a million people are declared bankrupt each year because they can’t pay the costs of their health care.[67] Life expectancy is four years lower than in the UK. The system is so inefficient that if the U.S. had a national health service like the UK’s, its health outcomes would improve and it would save almost 2.5 trillion dollars every year. Deaton and Case point out that the dysfunction in the U.S. health care system is, in monetary terms, more of a handicap than the reparations that Germany had t...

The Enlightenment has put some lucky people on what seems like a “perpetual path of progress,” but much of the world’s population lives in what must feel more like a dystopia.