“The lawlessness that continues at our southern border is fundamentally incompatible with the safety, security, and sovereignty of the American people.” April 4, 2018, President Trump on why he will deploy the National Guard to the US-Mexico border to stem the flow of asylum seekers from Central America.

What do we mean when we talk about the “people” of a nation, city, or community? And what do we mean when we purport to be acting in the best interests of those people? Through his words and his policies, US President Donald J. Trump has made it abundantly clear that in his view, the “American people” excludes a large proportion of those residing in “America.”

There are many ways to exclude people from a collective, and Trump has made use of virtually all of them. Certain people do not belong because they did not arrive on the nation’s soil in the sanctioned way; or they do not sufficiently embrace what Trump and his followers consider to be “American” values or customs; or they do not dress, work, eat, or speak like ‘Americans’; or they are members of the Democratic Party; or they are members of the press; or they are Muslim. Trump then frames the exclusion of certain US residents, and even citizens, from his understanding of the “American people” as a necessary step to protect and serve those people lucky enough to be included.

While his policies and rhetoric may be extreme, Trump’s way of thinking actually highlights a larger conceptual problem for anyone whose job it is to serve a large aggregate of people. As opposed to a specific person or persons whom one can name or touch, an abstract aggregate like “American people” is an inherently slippery, imprecise entity, the boundaries of which are highly dependent on the unspoken understandings of the particular person or persons defining it. Terms that public health professionals use to describe the abstract aggregates that they serve – like “local population,” or “community” – are similarly imprecise and open for interpretation.

This is the problem that lies at the heart of my book, Infectious Change: Reinventing Chinese Public Health after an Epidemic (Stanford University Press, 2016), which won the BSA’s 2019 Foundation for the Sociology of Health and Illness Book Prize. My book traces the long aftermath in urban China of the global response to the SARS epidemic of 2003. SARS was a novel flu-like virus with a high fatality rate that arose in southeastern China in the winter of 2002-03 and spread rapidly around the world, before disappearing just as suddenly several months later. Blamed for at first mishandling the epidemic by understating its threat and covering up local outbreaks, Chinese public health officials moved aggressively in the spring of 2003 to contain the virus’ spread. Under pressure to make sure that China would never again become the source of a global pandemic, the Chinese government then rapidly professionalized and expanded China’s public health system and infrastructure in the years following SARS – particularly in the southeastern part of the country known as the Pearl River Delta region, where scientists considered the threat of the emergence of another novel virus to be particularly high.

The Pearl River Delta region is known for its booming mega-cities, its cuisine, its hot humid weather, and its respiratory viruses. It is also known as one of the most popular migration destinations for China’s rural-to-urban migrant workers. During the 1990s and 2000s, tens of millions of people began rapidly emptying out Chinese villages in search of jobs, transforming the makeup of urban areas. Similarly to how Trump has portrayed transnational immigrants to the United States, in the urban Pearl River Delta this massive wave of migration has come to symbolize a frightening threat to the “native” population’s safety and wellbeing.

For the urban public health professionals that I studied, the Pearl River Delta’s enormous population of rural-to-urban migrant workers embodied a public health menace. Crowded into tenement-like housing and bringing with them what many urbanites considered to be unsanitary and “backward” habits, this so-called “floating population” was constructed as a threat to the clean and modern city that the Chinese urban middle class was committed to building. Chinese public health officials and professionals working in this region thus came to feel it was their duty to manage this perceived menace carefully in order to prevent another infectious outbreak, protect urban public health, and serve the “common good.” But who made up the “common” in this common good? Who were the people to be served?

When they talked about serving the common good, my interlocutors sometimes meant serving middle class, educated Chinese like themselves. Sometimes they meant the public health profession. Sometimes they meant the health of the globe, in all the abstraction that that implies. Rarely though did they mean the migrant population that they were charged, as public health officials, with governing. The population to be governed was not the same as the “common” to be served. I refer to this phenomenon as the “bifurcation of service and governance,” and suggest that it may commonly occur in any situation in which a small group of people in power is charged with serving a large aggregate.

I argue in my book that the distinction between “governing” a population and “serving” a community or “common”, while often glossed over by public health officials, can work to reinforce existing health inequalities along racial, ethnic and socioeconomic lines – or to produce new ones. Public health officials are obligated to defend the interests of those they serve – but they also frequently have their own ideas about who does or should count as being part of the collective whose interests are worth defending. Sometimes these ideas are codified, but often they are not. Whether through official policy, informal discourse, or mere innuendo, those who are considered antithetical to a community’s interests may be constructed as a nuisance or even a threat to those who belong, with longstanding consequences for the health of the excluded.

I am far from the first social scientist to point out the ways in which legal or social belonging, or a lack thereof, can produce or exacerbate health inequalities. But what was striking about the case of Chinese public health after SARS was the enormously inclusive language with which health protection actions that ultimately resulted in the perpetuation of inequalities were framed. The public health professionals I studied in China presented the threat of emerging infectious diseases not so much as a problem for Tianmai, or even for China, but as a global problem for the world at large. Preventing a devastating global pandemic was a project that would theoretically benefit us all and which should unite us all. And yet making the people of the world the target of protection and service ironically made the exclusion and demonization of people like rural-to-urban migrant workers even easier to justify and achieve. For whoever stands in the way of saving the world is clearly in the wrong, and the threat they pose needs to be eliminated. Or at least, that was the thinking in China in 2008-09 – and, I dare say, to some extent this is the same thinking that animates President Trump and so many of his followers today.

Combined Academic Publishers are offering a 30% discount on Infectious Change: Reinventing Chinese Public Health after an Epidemic.  Quote the discount code: CSA19ICH when you buy online.

Katherine A Mason, PhD is Vartan Gregorian Assistant Professor of Anthropology at Brown University and winner of the 2019 Foundation for the Sociology of Health and Illness Book Prize.