The Plague Cycle

by Charles Kenny

  Looking at overall life expectancy, in 1900, the average person born on planet Earth could expect to live to the age of thirty-three. By 2000, that expectation had doubled. Today, life expectancy is above seventy years—three score and ten.65 Citizens of the Central African Republic, the world’s poorest country, where about two-thirds of the population lives on less than $1.90 a day, have a life expectancy of fifty-one years—which certainly calls for boosting but, as a sign of progress, would have been enviable to most people living on the planet a century earlier.66

  * * *

  While developing countries are achieving levels of infectious disease rates that are far lower than those previously achieved by much richer countries, they’re also experiencing higher levels of noninfectious risk factors. Death rates from heart disease and hypertension aren’t rising solely because infection is on the decline and people have to die of something. It’s also that the spread of cheap calories and inactive lifestyles has gone global, too.

  In China, more people have jobs where they stand or sit still, and they can afford cigarettes along with a salt-, fat-, and sugar-filled diet including processed foods. As much as half of the country’s noncommunicable disease burden is related to such preventable factors.67 Forty percent of Chinese people aged forty-five to fifty-four are overweight, along with three-quarters of Mexicans and Russians—similar to levels in the US.68 Nearly 1.5 billion adults worldwide are either overweight or obese.69 And two out of five Earthlings have elevated blood pressure.70

  For all the challenges of postindustrial health, and the reality that setbacks such as Covid-19 will continue to emerge, progress against infection has been world-altering. The firestorm of disease set off by civilization has been tamed. For the first time in recorded history, urbanization and globalization are consistent forces for progress in health and quality of life rather than, at best, a mixed blessing and often far worse. And the truly massive health gains have had positive secondary effects vis-á-vis the role of women in society and the labor force, marriage practices, education rates, equality, declining violence, and a shifting global center of economic power.

  CHAPTER EIGHT It’s Good to Get Closer

  If you had to choose one moment in history in which to be born, and you didn’t know in advance whether you were going to be male or female, which country you were going to be from, what your status was, you’d choose right now.

  —Barack Obama

  The global merchant fleet (each line is a shipping route) sails free of the delays of quarantine. (Map from shipmap.org © Kiln.digital)

  The first stages of the sanitation and medical revolutions ushered in the last great victories of imperialism. While Napoleon’s global ambitions were derailed by disease, they were the last to suffer so dramatically: the course of the nineteenth century saw Europeans use infection-fighting tools to preserve their lives long enough to conquer. But globalization at the point of a gun remained bad news for the health of the colonized.

  Tropical imperialism relied on all three strategies of exclusion, sanitation, and medication. Exclusion played a role in the theory that whites were primarily—or even exclusively—infected by native populations. The “father of tropical medicine,” Sir Patrick Manson, felt that segregation was “the first law of hygiene.”1 Sanitary approaches included draining swamps around towns and camps and moving colonists into hill towns. These were responses to the threat of miasma that (nonetheless) reduced the risk of infection.

  Then, in 1820, two French chemists isolated quinine—the active ingredient of fever tree bark that had been traditionally used to treat malaria. Six years later, twenty crewmen of the HMS North Star landed in the malarial death zone of Sierra Leone. All but their lieutenant took a daily infusion of fever tree bark in wine, and all but their lieutenant remained healthy. By 1858, the Botanical Gardens at Kew in London was leading a global effort to transport fever bark plants and seeds out of the Andes to plantation sites at Kew, Calcutta, and the Nilgiri hills of India, Singapore, and Java.

  And in 1880, enough quinine was being produced to provide 10 million patients with a daily dose.2 The English rapidly developed a quinine “tonic” water that they drank with gin and lime. It was both more bitter and sweet, as well as considerably warmer, than the version we drink today, providing more evidence of global progress over time.3

  In 1830, French troops occupied a strip of the North African coastline in modern-day Algeria. Death rates from malaria were initially crippling—as they were among other European troops on the continent—but they began to fall in the face of swamp-drainage and quinine prescriptions. The annual malaria mortality rate dropped from sixty for every thousand people to less than one for every thousand.4

  Mortality rates for Europeans across the tropics fell even further once the link between mosquitoes and malaria was demonstrated in 1898, and that between mosquitoes and yellow fever was shown by Walter Reed of the US Army in 1900 (the latter thanks to experiments involving brave volunteers who agreed to be bitten by mosquitoes that had recently fed off yellow fever sufferers; the transmission path was demonstrated when they then fell sick themselves). After that, spraying larvicides was added to the mix of interventions against tropical disease.5

  The result was rapid: in 1875, the year that Henry Morton Stanley started his voyage of exploration down the Congo River, only three European imperial powers had colonies on the continent, largely limited to coastal areas. By 1914, more than 90 percent of the continent had been claimed by colonizers.6 Algeria alone was home to more than half a million colonists by 1900.7

  From coastal strips one hundred years earlier, British control extended, by 1914, over the entire Indian subcontinent from modern Pakistan through Bangladesh and Burma down through Malaysia and Papua New Guinea. In Africa, the British Empire occupied a swath of territory from modern Egypt and the Sudans through Kenya, modern South Africa, Zimbabwe, Zambia, and Malawi, as well as Nigeria and Ghana. The American empire expanded as well, critically dependent on mosquito control. Spraying pesticides was an important reason that the US was able to finish construction of the Panama Canal—in contrast to the French, who’d failed a quarter century before after suffering appalling casualties.

  In India and Africa, quinine and swamp drainage remained too expensive for European imperial authorities to consider as practical tools for lowering native mortality.8 Protected colonists behind their cordons sanitaires, sipping gin and tonic under the netting, could ignore the death toll and the disease risk of forced labor and mass movement faced by Indians and Africans.9

  Morton Stanley, explorer of the Congo, was famed for uttering the words “Dr. Livingstone, I presume?” on meeting his fellow explorer near Lake Tanganyika—although he probably made up the quote sometime later for the readers of the New York Herald. Stanley was widely reviled for his treatment of African porters—making him a perfect partner for Belgium’s King Leopold, whose private empire in the Congo Basin (the current-day Democratic Republic of the Congo) used slavery and violence on a massive scale to tap and export rubber. But the explorer’s biggest contribution to misery on the continent may have been an accidental one: spreading sleeping sickness across the heart of Africa.

  Sleeping sickness is transmitted by the blood-sucking tsetse fly—which picks up the protozoan parasite along with a meal from an infected human or animal carrier. When it buzzes on to its next unwilling host, the tsetse deposits thousands of parasites into the bloodstream. As they multiply, the victim suffers confusion, mood swings, and overwhelming exhaustion. Eventually the infected person may fall into a troubled sleep, thence to a coma and finally to death.

  The sickness had been known in parts of West Africa from the 1300s, and health economist Marcella Alsan argues that its deadly effect on animals was a significant deterrent to agriculture, the development of centralized states, and, through those effects, modern economic performance.10 But much of the continent (including precolonial empires like Great Zimbabwe) remained infection free u
ntil the end of the nineteenth century. The tsetse fly was already there. All that was required was a sufficient number of infected visitors to start up the cycle of sickness.

  And in the employ of King Leopold, Stanley provided the hosts. He set up stations along the River Congo in the early 1880s. Explorers, plantation managers, and traders—with their porters and guards—started traveling up and down the river in increasing numbers. By 1904, the New York Times reported thirty thousand sleeping sickness deaths in villages around Lake Victoria. The newspaper, focusing on what mattered, declared the disease “a terrible evil that is beginning to oppose a powerful barrier to… colonial enterprises in tropical Africa.”11

  In French West Africa, meanwhile, universal conscription and “corvee labor” (temporary enslavement by the colonial government in lieu of tax) ensured the further mixing of disease pools. Voluntary and involuntary migrants died in the tens of thousands as they were exposed to local varieties of infections, including malaria. And returning workers carried the new strains back home, where they killed yet more people.12

  In India, railroads—and the workers who migrated to build them—spread cholera. Farmworkers migrating to tea plantations spread hookworm, while large-scale rice plantations fostered malarial mosquitoes. Migrant workers in mines were particularly at risk of tuberculosis—and also spread it back to their homes when they returned.13

  Only with the spread of, first, new technologies of infectious disease control and, second, postcolonial governments at last prioritizing the health of the majority did life expectancies begin to rise in earnest in the developing world. An important dividend was that city living and global travel became safer for everyone. Victories against infection allowed the world to get closer, which proved a vital spur to innovation. But it also radically reshaped demographics, refuting Malthus’s predictions about what happens when people get rich and live longer.

  * * *

  With the medical advances of the twentieth century, cities worldwide finally became healthy enough to expand. In many of the world’s poorest cities today, most urban population growth is due not to migration but to city residents having children that survive more often. Looking at recent survey data, Nobel Prize–winning economists Abhijit Banerjee and Esther Duflo found that, among the world’s poorest—those who live on less than a dollar a day—infant mortality rates in urban areas were lower than rural rates in two-thirds of the countries for which they had data.14 That slum living in many developing countries is healthier than the rural alternative is a complete reverse of the global situation a century ago.

  That helps to account for the global growth of cities. In 1960, 1 billion people lived in urban areas worldwide. Today that’s closer to 4 billion—the majority of the world’s population. In 1800, Tertius Chandler’s city population data reported one city (Beijing) with a population of more than 1 million people. By 1900, that had reached 16 such cities. In 1950, the United Nations listed 77, well under one-half of which were in what might generously be considered the developing world at the time. The UN suggests there were 501 cities with more than 1 million people by 2015, the overwhelming majority in the developing world.15

  Urbanization has always been a key to economic dynamism. Concentrating economic activity in cities makes it easier to transport goods from producers to consumers. Having many people in the same place allows workers to specialize. Economist Edward Glaeser points to the Yellow Pages: if you want a store that specializes in necktie restoration, you’d better hope you are in a major metropolis. Or if you want a doctor that specializes in rare diseases, look to a place likely to hold enough patients.

  And urban areas are the centers of technology advance because entrepreneurs and inventors learn from one another. In the US, 96 percent of new product innovations occur in metropolitan areas, with nearly one-half of the total in New York, Los Angeles, Boston, and San Francisco alone. The advantages of agglomeration also help to explain why workers who live near a city that employs more than half a million people earn a third more than those outside a metropolitan area.16

  It isn’t just the US: the half of the world’s population that lives in urban areas generates more than 80 percent of global output, while 600 cities that account for just one-fifth of the global population generate more than 60 percent of global output.17 Urban living is also healthier for the environment as it tends to involve less travel and smaller housing.18 Add to that the fact that urban dwellers are ideologically different from their rural counterparts: comparatively liberal, international, trade- and migration-loving, in favor of gender equality and gay rights, environment-defending, and open-minded in matters of religion.19 The city is progressive—and it’s where progress happens.

  * * *

  Just as getting closer allows for greater specialization and innovation within cities, global connectivity allows for specialization and innovation across countries.

  To see how much the sanitary and medical revolutions have changed the risks of global interaction, examine what kills Americans abroad these days: cardiovascular events including heart attacks account for 49 percent of all deaths, injuries for a further 25 percent, and infectious diseases other than pneumonia for just 1 percent. Of course, most US travel is to places where infectious disease risk for Americans has long been comparatively low, but even travel to pathogen-rich environments has become far, far safer than it used to be: a study of 185 deaths of US Peace Corps volunteers, placed in some of the world’s least healthy countries, found that unintentional injuries and suicides were far more deadly than infection, accounting for more than 80 percent of deaths between them.20

  The same applies to Chinese engineers traveling to Malawi to help build a road or Brazilian executives flying to Laos to ink a commercial agreement. And while outbreaks from cholera to Covid-19 demonstrate travel still spreads diseases, each individual traveler usually faces a very small risk of being the victim—or cause—of a new outbreak. Modern medicine, along with improved sanitation when it is available, has made international travel pretty much as safe as staying at home—a massive change from two hundred years ago.

  That has been a huge force behind globalization. We’ve seen that high-infection environments foster closed social networks and distrust of strangers. Similarly, declining risk of infection leads to greater openness: for example, psychologist Julie Huang has found that vaccinated test subjects, when they’re reminded of disease threats, are less likely to show prejudice against immigrants than unvaccinated subjects.21 Not surprisingly, when people have few worries about getting sick, they’re more willing to travel and trade, welcome strangers, and try new things.

  Looking at the US, the total number of travelers taking an ocean journey overseas from America in the year 1820 was around twenty-one hundred—or 0.02 percent of the population. By 1960 (adding in long-haul air flights), that had reached a little less than 1 percent of the population. At the turn of this millennium, the annual number of US international travelers as a percentage of the population was 9 percent, involving nearly 25 million trips a year.22 Worldwide, in recent years, 1.2 billion people have traveled internationally as tourists each year (2020 will be a tragic exception, of course).23

  Transport technologies have made travel considerably cheaper, but that level of movement only occurred because the fear of the foreign and the reaction of exclusion was on the decline. Tourists with two weeks’ holiday a year would likely be deterred by a quarantine period three times that long, and so would business travelers or scientists headed to an international conference. That’s to say nothing of people deterred by the risk that travel would kill them. Plus, permanent migration is easier in a world where infection isn’t a reason to exclude. That’s particularly good news for health services in rich countries: nearly one out of every three physicians and surgeons in the US is foreign-born, along with a quarter of the health aides, a fifth of the lab technicians, and half the medical scientists.24

  Safer travel makes it easier for people to s
cout opportunities, make deals, and set up operations—even in the Age of Zoom. Think of what’s involved, for example, in running more than twenty-four thousand Starbucks stores in seventy countries, or managing some other part of the $6 trillion worth of US foreign direct investment worldwide.25

  The story is the same with trade: it can’t happen without global movement of people—sailors, pilots, marketers, and salespeople. In 1820, the United Kingdom exported goods worth $53 per inhabitant. By 2003, that total had reached $5,342—a hundred-fold increase. The corresponding figures for the United States are $25 and $2,762—an even faster growth rate.26 Nearly 10 million US workers directly depend on exports for their jobs. About one-sixth of everything Americans buy comes from abroad.27 And the US is one of the least globally integrated countries in the world.

  Trade allows countries to specialize, including when it comes to medical supplies. For example, the US is the world’s largest importer of personal protective equipment: the country imports far more respirators, gloves, and goggles than it exports. But it also exports more hand sanitizers and face shields than it imports.28 And finished products—respirators or ventilators, for example—are made up of components from lots of different countries. Trade enables the US and the rest of the world to get vital medical equipment at a far lower cost than if everyone produced it all at home. It’s why early efforts to restrict trade in that equipment in 2020 were a tragic mistake for everyone.