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How pandemics shape social evolution

Laura Spinney weighs up Frank Snowden’s sweeping history charting the impact of infectious diseases on society.
Laura Spinney is a science writer based in Paris. Her most recent book is Pale Rider: The Spanish Flu of 1918 and How it Changed the World.

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Illustration by Antoine Dore

Epidemics and Society: From the Black Death to the Present Frank M. Snowden Yale University Press (2019)

When will we learn never to declare the end of anything? Only 50 years ago, two prominent US universities closed their infectious-disease departments, sure that the problem they studied had been solved. Now, cases of measles and mumps are on the rise again in Europe and the United States, new infectious diseases are emerging at an unprecedented rate, and the threat of the next pandemic keeps philanthropist Bill Gates awake at night.

So it’s a shame that to make this point, Epidemics and Society, Frank Snowden’s wide-ranging study on this rolling human reality, repeats the urban myth that in 1969, US surgeon-general William Stewart said, “It is time to close the book on infectious diseases, and declare the war against pestilence won.” Even though Stewart never said this, it’s clear that there was a pervasive, dangerously complacent attitude in the late 1960s. International public-health authorities were predicting that pathogenic organisms, including the parasite that causes malaria, would be eliminated by the end of the twentieth century. Snowden’s broader thesis is that infectious diseases have shaped social evolution no less powerfully than have wars, revolutions and economic crises.

It’s not a new message, but it bears repeating. Snowden, a historian at Yale University in New Haven, Connecticut, has assembled a vast amount of evidence, some the fruit of his own research. His global history spans more than a millennium of outbreaks, covering diseases from bubonic plague to smallpox, malaria, the respiratory illness SARS, Ebola and beyond. He rehashes the long history of scapegoating, violence, mass hysteria and religiosity that have accompanied epidemics, but only to speculate on their longer-term social, political and cultural consequences.

When cholera struck Paris in 1832 — in an epidemic that eventually killed nearly 19,000 Parisians — a conspiracy theory spread that the unpopular government under King Louis Philippe was poisoning wells with arsenic. The police and army were barely able to contain the violence that ensued. The institutional memory of those events fuelled dread of the “dangerous classes”: poor people. That, Snowden argues, might help to explain why the two most egregious examples of class-based repression in the nineteenth century also took place in the French capital. These were the violent crushing of the 1848 revolution and the bloody destruction of the Paris Commune, the revolutionary government that briefly ruled the city 23 years later.

The synergy between wars and epidemics in shaping history has long been recognized. Napoleon Bonaparte’s nineteenth-century imperial expansion westwards across the Atlantic Ocean was halted by yellow fever, which his army encountered in France’s Caribbean colony of Saint-Domingue (now Haiti). His eastern ambitions were thwarted by dysentery and typhus. (The typhus epidemic that ravaged the Grande Armée during its retreat from Moscow might have prompted an unparalleled die-off by some measurements, as Snowden claims. But it was surely not in terms of “deaths per capita”.)

Security threat

An odd omission from the book is the 1918 ‘Spanish’ influenza pandemic, which overlapped with the First World War and is estimated to have killed between 50 million and 100 million people. Snowden might have felt that it garnered enough attention around its centenary. But a future flu pandemic is currently ranked among the leading threats to global security, and there has been surprisingly little research on the long-term consequences of the 1918 catastrophe. Furthermore, it might have been interesting to explore the possible links between that pandemic and the ongoing epidemic of AIDS in South Africa, which the book does cover.

There is evidence that white scapegoating of black South Africans in 1918 precipitated the first legislative steps towards apartheid. As Snowden discusses, by restricting the land available to people of colour, apartheid accelerated the growth of a migrant labour system that divided black families. It also encouraged new forms of social and sexual behaviour. Both developments, in turn, hastened the spread of AIDS once it arrived. Young men growing up away from their families, for instance, often developed standards of masculinity that promoted sexual conquest and violence; South Africa now has one of the highest rates of rape in the world (K. Naidoo S. Afr. Med. J. 103, 210–211; 2013). The crowning tragedy of these depressing events was President Thabo Mbeki’s endorsement, from 1999, of a US AIDS denialist’s theory that the disease is not caused by the HIV virus. That resulted in the avoidable deaths of an estimated half a million South Africans.

In the twenty-first century, we seem to be repeating many of the mistakes that triggered or exacerbated epidemics in the past. That is presumably why Snowden refers ominously to this century’s first major epidemics, of SARS and Ebola, as “dress rehearsals”. Although many people espouse health care for all, our globalized economic system militates against it — because profits are rarely invested where they were extracted — and we still seem to think that borders will keep disease out, even though they never have. Since Snowden completed his book, the administration of US President Donald Trump has announced that an immigrant’s chances of getting permanent residence will now be linked to the burden they put on the public purse — including health-care costs. That makes it more likely that recent arrivals will avoid doctors, and infectious diseases will go undetected.

The starkest reminder that the battle is not won, however, is that only one infectious disease has been eradicated globally: smallpox. Others that those optimists of the 1960s thought would have vanished by now have been hard to dislodge — and could easily flare up again. The strife-ridden Democratic Republic of the Congo is harbouring more than Ebola. There is also a measles outbreak, and a circulating strain of polio that mutated from the live, weakened one in the oral vaccine. There have been successful local disease eradications, but they often came at a price. A sustained campaign of DDT application helped eliminate malaria from the Italian island of Sardinia by 1952, for example, but in 2001, the pesticide was banned globally under the Stockholm Convention, after it was found to be dangerous to wildlife and the environment.

For Snowden, the lesson from more than 50 years of such experiments — successes and failures — is that eradication is most likely to work when doctors, politicians, drugmakers, the media and citizens work together. Salus populi suprema lex, he reminds us: public health must be the highest law. He has preached that message to generations of Yale undergraduates, and repeats it in this book. The risk is only that he is preaching to the converted.

Nature 574, 324-326 (2019)

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