What a Horse Flu Reveals about Societies at the Dawn of Industrialization: In Conversation with Thomas G. Andrews about The Great Horse Flu

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This fall, Thomas G. Andrews, a University of Colorado Boulder environmental historian and director of the university’s Center of the American West, releases his third monograph, The Great Horse Flu: A Forgotten Contagion and the Fate of Reconstruction America. The book tracks a novel equine influenza strain that originated north of Toronto in 1872 and eventually infected more than ten million horses, mules and donkeys across North and Central America. This disruptive event offers fresh insight into the workings and inequities of societies in the Americas at the dawn of industrialization. NiCHE editor Mary Baxter recently chatted with Andrews over Zoom to discuss transnational history, border politics, and writing about a historical plague in a post-COVID world. This interview has been edited for clarity and length. The interview is also available on YouTube and Spotify.

Mary Baxter: What prompted your interest in writing about this flu?

Thomas Andrews: Other historians have written about the flu here and there. For the most part, they focused on an urban history story about continuing human dependence on equines and mentioned the flu a few pages in, sort of like, “Oh, isn’t this strange that this happened?” When I started to look into it more deeply, I realized that there was a bigger story, and not just an urban one or simply concentrated in the Northeast United States.

This outbreak really exploited a fundamental vulnerability, a fundamental dependence of humans in all of these places on horses, donkeys, and mules during the early 1870s. Whether we’re talking about urban societies or rural ones, whether we’re talking about agricultural regions or mining regions, whether we’re talking about settler states or Indigenous nations, equine power was crucial.

Like most disease outbreaks, this one provides what we might consider a natural experiment. We get to see the same virus hit different places and different things happen. As a historian, that’s always interesting. There’s a comparative dimension: How is this different in the city versus the country? How do Mexicans respond to it differently than Americans? Also, it’s an outbreak that tells us something really important about a virus, influenza, that we live with all the time.

I started this book in earnest in 2018. A large chunk is shaped by and in dialogue with questions that the COVID pandemic of 2019-2023 generated for me. When I look at this equine influenza outbreak in the early 1870s, it’s a super bug in its own right. The outbreak probably infected 95 to 99 per cent of horses, donkeys, and mules and killed one to four percent of them. So there’s an important reminder here of what influenza is capable of. That in turn leads to a better understanding of how emergent zoonotic diseases—diseases that circulate back and forth between humans and other animals—fit into history, and also how history can help us better understand the world that we’re in and a world in which these outbreaks are becoming more and more impactful and influential and frightening.

The front cover of Thomas Andrew's new book in red, black and white. The top half shows a filtered photograph of two horses in harness drinking from a public water trough and the title of the book appears below.

Baxter: Two main protagonists, the virus and the equids, can’t speak for themselves. What research, methodological and theoretical challenges did you encounter to tell their stories and how did you resolve them?

Andrews: I ran into the standard challenges in environmental history and animal history—how do you get the perspective of entities that don’t leave direct sources?

With viruses, there’s still continuing debates over whether they are actually living things. Philosophers go into that, but even certain kinds of biologists are not convinced that viruses possess the qualities of life. And most historians think that agential entities probably need to be alive. Viruses are on that boundary.

Also, nobody at the time was testing these horses. They lacked the capacity. So I’m making inferences about what the pathogenic agent involved even is. People at the time commonly said it was influenza. I can compare their diagnoses with diagnoses today. But there’s not really much physical evidence in terms of remnant viruses from this time period.

I really had to do a lot of interdisciplinary digging. I drew upon a lot of present-day scientific understandings and tried to read evidence from the past in light of those understandings.

There’s some big assumptions that I can’t say are rock solid. For instance, historians of disease, at least the extremely historicist ones, argue that these agents change so much or that any evidence of them is so filtered through human experience that we can’t actually know the entity itself. That’s not really a view I subscribe to in the book.

At the end of the day, [that lack of precise evidence] was often pretty frustrating. I wanted to know what this was like for the animals involved. How did they actually respond to it? I could do a fair amount of reading against the grain. People at the time often cared a lot about horses. These creatures were central to their lives in all sorts of ways, and some folks were pretty observant. So fortunately, this event was recorded in enough sources—journalists, for instance—that I could find vivid scenes of animal suffering that helped me get at some of the more affective or emotional sides of this story.

Baxter: In Killing For Coal: America’s Deadliest Labor War, you focused on a specific event as a way to explore the past. You’re doing the same thing here. What attracts you to exploring history through a particular event?

Andrews: I like how the event provides a central focus. I really like to think cinematically—I like to do the flashbacks and, less often, but still sometimes important, the flash forwards—and the opportunities for shifting the lens, and also for going deeply into context when I think that it’s really important. Maybe I might be a bit of a control freak as a historian, and I think that there’s something about having a central event that gives me opportunities to play with things in the past and to make choices about what I want to go into.

My other book, Coyote Valley: Deep History in the High Rockies, does not have a central event. It explores the long-term environmental history of a particular place on the landscape. And in that project, the lack of a central issue or a central question–a central thing I was trying to explain–made it a lot more difficult. In some ways, the question that inspires The Great Horse Flu or motivates it throughout is what can we better understand about North America in general and the United States in particular by taking this unexpected and unusual point of departure?

So this novel virus appears, it affects a crucial species to humans, and then what can we learn through its unfolding about something like Reconstruction or the ways in which Chinese Americans in San Francisco were trying to continue to carve out spaces for themselves in the United States using the opportunities the 14th Amendment provided for them? The event helps me cut to the heart of what I find interesting.

Baxter: You use a relationship between two elements—animals and the novel virus—to actually speak about something else, North and Central American societies. It’s like you employ two layers of lens, almost like GIS only it’s layers of historical analysis.

Andrews: I actually did create a GIS. I haven’t published it yet, but the book is going to have a companion website that’ll make that—the data and the maps from the GIS—available. To go into the layers metaphor, I think there’s all of this invisible or barely visible activity and labour and exertions of energy that [are] constantly creating and recreating the world as we know it. Yet most historians don’t pay attention to that. Even when we’re looking at environmental history, that activity is a little too granular and a little too gritty for a lot of scholars. But I find that stuff fascinating. For instance, that we have a virus that first evolves in the area of Scarborough and York and Markham Township (inland from Toronto) to me indicates that it was probably a novel variant. So the question becomes, “how can a new form of a virus spread in this past world and what does the pattern of spread show us?”

Most of my evidence here comes from digitized newspapers, and those digitized newspaper accounts allowed me to see that sometimes people at the time said the disease seemed to arrive with this particular group of horses that were unloaded from a boat or unloaded from a stock car on a train. But there’s all sorts of other instances where there’s no sense of when this thing first arrives. This is something COVID really helped me understand—there’s stories here of super spreaders.

There’s stories of long-distance transport, but the main way this virus spreads is just from horse to horse to horse. The fact that the disease could cover a dozen, sometimes two dozen miles a day tells us something really important about how dense the equine population is, how interconnected it is, how all those daily interactions between humans are creating interactions between animals that are making it possible for a virus to move from one host to the next.

Image caption by Thomas G. Andrews: The panels of this full-page illustration vividly depict the disruptions the Great Horse Flue caused. Note the close focus on a succession of street scenes, with goods accumulating, onlookers gawking, and humans and oxen doing their best to provide the motive power that flu-stricken horses could no longer perform. Theodore R. Davis, “The Horse Plague,” Harper’s Weekly, November 16, 1872, 900. Courtesy of University of Colorado Libraries.

Baxter: You mentioned a website and GIS. What’s going on there—what did the spatial data reveal?

Andrews: The NIH National Library of Medicine, which provided a grant that helped fund the book, also provided funding to generate a database and animations. I had graduate students who knew a lot more about GIS than I do, and they were able to use this [data] to generate heat maps, that kind of thing. That then helped my team generate visualizations of how this outbreak spread. That helped to reveal how extensive this outbreak was, as well as some of the more unexpected aspects of its behaviour.

Another thing that the maps really reveal nicely is that the virus behaved differently south of the U.S.-Mexican border. In the U.S., it really does behave in a fairly wave-like fashion, especially east of the Rockies. South of the U.S.-Mexico border, its movements are chaotic. I think that’s because Mexican equines were not very well connected. That disconnect tells us something important about the state of the Mexican economy and the lack of national integration in the early 1870s.

West of the Rocky Mountains, there’s a different story which the maps support to some extent. This is an outbreak that spreads most quickly in the U.S. and Canadian Wests, through corridors of settlement, and that backfills into Indian country. One of my chapters explores why this would be the case.

Western native peoples were highly dependent on horses during this time period. One might expect that along with the idea that native peoples were especially vulnerable to human diseases during this time period, this outbreak would move quickly through Indian country and that it would cause huge problems. What I argue is that it actually got there slowly. It doesn’t generate much evidence. I think to some extent that’s about the other challenges that Native North Americans were facing by the early 1870s.

I think there’s also some important insights there about how human population declines driven by conquest, starvation, demobilization and a whole host of other factors—infectious diseases, expropriation–all of these things–actually reduced horse populations. Meanwhile, you have colonial policies from the U.S. and Canadian governments trying to cut down on raiding and other forms of equine exchange.

There’s also limitations to using GIS, as there is with any technique. Further west in North America, for instance, newspapers just weren’t published in the early 1870s in that many places, and, given the sort of expansiveness of the terrain, heat maps break down over there. The geographic component doesn’t always answer questions, but it provides other lines of evidence for some dynamics that are really fascinating and important and not always easy to see without that kind of spatial attention.

Baxter: It makes me think about our conversations as a society and, as historians in this moment in time, about the use of AI and questions about transparency and accountability. Here you are addressing these questions with digital technology, which I find interesting because not all that long ago, these were the conversations we were having about the use of digital tools, and now we take these tools for granted. What are your thoughts?

Andrews: This topic could not have been an analog history, and the limitations of the existing literature on this were partly connected to the limitations of analog history. Most newspapers from this time period are not digitized. Many of the ones that are digitized are behind barriers that I was not able to or not willing to transcend. At the same time, though, I am abundantly aware that by the end I had accessed at least 6,000 articles that had substance on this outbreak, which is a fair amount, but still a drop in the bucket.

To circle back to AI, one of the things that’s always important about getting people who are interested back to the primary sources is that there’s more in there. One of the things that I find interesting about trying to add sixty, eighty primary source accounts on the website, is that there are things in there that I didn’t find interesting or things that I didn’t find worth exploring, but that doesn’t mean somebody else can’t do really fascinating stuff with them. I also think this actually would be a pretty interesting experiment: what sorts of AI prompts could you use on these bodies of evidence and how would the understandings that might generate interact with the ones that I came up with?

Baxter: This book is partly a borderlands history. What are your thoughts about doing a borderland history in an age where borderlands have become so highly politicized?

Andrews: As far as the ways in which the book is borderlands history, I think that there’s a fair amount on humans, animals, and pathogens that cross borders. And that starts early on in the book with Ontario in many respects being an outgrowth of the American Revolution, with early settlement in the area where the novel form of the flu seems to evolve. It’s [British] loyalists needing a new place to be. And there’s all sorts of livestock and poultry crossing borders, crossing oceans, probably contributing to the mix of strains that this strain emerges out of. There’s a lot here about movements, migrations, trade, borders.

When the outbreak really gets underway and when it starts moving toward the United States, you see belated and really just feeble efforts by the U.S. government to try to intervene, to try to impose quarantines. I think we learn something pretty important about the American state at that time, which is that it lacks any capacity to handle this situation. And it doesn’t try very hard, and there aren’t recriminations. One of the things that this book teaches about borders is there’s some interesting things there about change over time and continuity.

Massive changes in borders have since taken place in infrastructure, border surveillance, border control. There are continuities, though, with this is a particular kind of illness. It’s an upper respiratory virus, low fatality, very high infectiousness–not unlike COVID. Even in our highly militarized border regime, these viruses are still going to get across.

They’re not worth the trouble to stop, which is what people in the 1870s thought. The portion of the book on how the outbreak unfolds in San Francisco gets at some of the ways in which large-scale disease outbreaks, even ones of animal diseases, create opportunities for racialization, race-making and race-based restrictions.

Clearly that’s always been a dynamic in human history. I think that we can safely predict that these issues are not going to get better in the world we’re in right now. COVID showed this in various ways.

Subsequent outbreaks, such as Ebola in the Democratic Republic of the Congo and Uganda also speak to the importance of thinking about human history as more than human. These outbreaks create disruptions that provide opportunities for really bad things to happen oftentimes.

Featured image caption by Thomas G. Andrews: Adoniram B. Judson, son of famous Baptist missionaries, Union army surgeon and physician for New York City’s Board of Health, mapped information on the outbreak’s spread that he gathered from newspapers and correspondence. The result is a masterful example of the emerging techniques of epidemiological cartography. Note how Judson’s map pinpoints the epizootic’s initial emergence outside Toronto and plots is subsequent month-by-month spread. Image: Adoniram B. Judson, “History and Course of the Epizootic Among Horses upon the North American Continent,” American Public Health Association Reports 1 (1873):88. Courtesy of HathiTrust.

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Mary Baxter

MARY BAXTER, is a PhD candidate in The Department of History at Western University and a journalist and editor. She specializes in the history of the Great Lakes region and in issues to do with agriculture, rural affairs, the environment and southwestern Ontario.

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