Soon after the global SARS outbreaks in 2003, and many years before the current novel coronavirus pandemic led to a historically unique shutdown of global air traffic, health experts anticipated the vital role air connections would play in the likely event of a worldwide zoonotic pandemic. In 2006, for example, the chief doctor at Frankfurt Airport observed, “In the context of globalization, we in Europe must assume that infection outbreaks on other continents will within 14–24 hours pose a considerable threat to our German population.”1 For medical and global historians, past relations between air traffic, plagues, and health policies present a promising, still largely unexplored research topic.2 Stranded last spring due to a COVID-19 flight ban myself, I started wondering how experts in epidemiology and sanitary control reacted to the rise of mass air travel. How did health experts cope with the breakthrough of the jet age in the 1960s and what were their strategies against the spread of contagious diseases by airplanes?
Without attempting to offer a full-fledged answer, I look at some early control practices and the limits they faced, based on a sampling of sources from German archives. Using the example of smallpox, the first major epidemic threat that commercial passenger aviation confronted, I stress the critical role that not knowing played in the development of early anti-epidemic strategies in air traffic. By this I mean more than medical uncertainties. I am particularly interested in health experts’ initial lack of knowledge about individual mobilities in an increasingly complex and global traffic network and how they became aware of these critical unknowns.
Mobility does not constitute the only factor in the spread of contagious diseases, but it is a powerful one.3 Knowledge about this causal link was produced long before epidemiologists used modern scientific methods. In the late Middle Ages, ship quarantine was a common measure in Western Mediterranean seaports before the practice spread around the world under the trade-based maritime empires of the early modern period. Movement over land fell under sanitary control as well. In the eighteenth century, the Habsburg empire added quarantine stations to its fortified border on the Balkans. The outcome was a cordon sanitaire at which travelers from Ottoman lands had to wait for several weeks before they could finally move on.
As a strategy of disease control, quarantine responded to the lack of knowledge about whether mobile bodies were carrying diseases. If it only required a temporary stop, it nonetheless slowed mobility. In that, it clashed with developments in global transport since the nineteenth century. The invention of fast transport technologies like steamships meant that even long-distance destinations could be reached before passengers showed any detectable symptoms. This effect multiplied during the second half of the twentieth century, when most passenger traffic shifted from ships to airplanes. Already in 1938, a flight from India or Russia to London took several days less than the average incubation period of smallpox and typhus.4 As a German doctor summarized in 1968, “In the past, the long sea routes from Africa and Asia would have filtered out all smallpox cases at the latest when arriving at the Port Said quarantine station, since 1946, however, the first airborne introductions have occurred.”5
Along with the increasing speed and frequency of long-distance mobility, its economic value explains why, since the mid-nineteenth century, extensive prophylactic quarantine had fallen increasingly out of favor, especially in the British Empire. In an age of free trade and commerce, confinement seemed archaic and bad for business.6 The same applied to the new phase of trade openness in the rising age of mass air traffic after World War Two. The International Sanitary Regulations of the World Health Organization (WHO) from 1951 that covered air transportation had the main aim of promoting “maximum security against international spread of disease with minimum interference with world traffic.”7 Consistent with the paradigm of liberalism, international conventions under the United Nations reinforced the doctrine that the flow of commercial traffic had to be protected from the costly burdens of preemptive controls and delays.
While quarantine and isolation had become a last resort, other sanitary measures were needed to cope with the epidemiological uncertainties of mobility in the jet age. One of the first major health problem for global air traffic occurred at the turn to the 1960s. Smallpox, among the most dangerous infectious diseases, was deemed as good as eradicated in the global North toward the mid-twentieth century. Between 1950 and 1973, however, the disease was reintroduced into European countries on about fifty separate occasions.8 Local outbreaks occurred in West Germany in the late 1950s and early 1960s. Public health experts and the media immediately saw a link between those incidents and the “flying pox carriers,”9 as the German weekly Der Spiegel dubbed the airplanes. Indeed, from 1959 almost all incidences of small pox in West Germany traced back to air travel.10 Crossing world regions and imperial borders, air routes created tightening links between Germany, via the transit hub in Frankfurt, and regions in the (post)colonial world where smallpox was endemic, like India and Pakistan. In West Germany and other affected countries, authorities reacted by trying to turn airports into “epidemic barrier[s]”11 against what they perceived as threats from the “underdeveloped” global South. They still used quarantine for the cases that inevitably turned up; however, their main tool became vaccination control.
Just like quarantine, vaccination was a preventive measure that compensated for not knowing if a person traveling from a risk area was infected or not. German border guards at the airport asked passengers arriving from Asia, Africa, and South America to present valid immunization records for smallpox and, where required, requested them to get revaccinated immediately.12 Yet this strategy faced serious limitations. Enforcing compulsory vaccination was not always possible and ultimately depended on the cooperation of the passengers.13 Thus, in some countries, including West Germany, the United Kingdom, and the United States, health authorities appealed to people’s sense of personal responsibility. They distributed warning cards asking travelers to submit their contact address to the authorities, to monitor their own health, and to see a doctor if necessary.14 Such dependence on individual cooperation, however, was not the only reason why the idea of turning airports into national disease barriers against the “Third World” failed. Another was the very nature of air mobility itself.
Air mobility in the 1960s, much like today, was not an assemblage of distinct linear movements but instead a jumbled network that included unaccounted-for movements. Often passengers travelled via transfer and transit stops. When a plane arrived, a West German official remarked in 1962, the routes of its passengers were not always clear; they might have changed planes abroad, and in fact come from “Asia etc.,” even though the flight they arrived on was from London, for example.15 Similarly, a British expert reported that all travelers arriving from the Indian subcontinent had to undergo strict vaccination controls in London, but 33 percent of them transited in Amsterdam, Paris, Frankfurt, or elsewhere in Europe and were thus hard to identify.16 Besides the old problem of not knowing whether or not passengers from a risk area were carrying a given virus (an already known unknown, so to speak), there was thus a new uncertainty. Experts and officials started to realize that they lacked reliable knowledge about whether or not passengers were even coming from a risk area, let alone if they had come in contact with someone who was.
One solution to this problem that West German health experts envisaged was the introduction of landing cards. To be filled out by every passenger arriving at a European airport, the cards would collect data about the travelers’ whereabouts in recent weeks, their final destination airport, and their address during the next fourteen days.17 Although cards like these were actually introduced in West Germany in the late 1960s, they never gained full acceptance and were soon abolished. Dependence on the cooperation of the passengers, who did not always fill out the cards correctly, was an issue. Economic motives played a role as well. Transport experts of the German government, airlines, and other stake-holding companies and organizations, including the International Air Transport Association, complained that such methods were ineffective and an unnecessary complication to travel.18 Even proponents of the arrival cards had to admit that the results were not fully satisfactory.
One major shortcoming of the card system lay with the intricacies of networked air mobilities that the cards did not take into account. Tracking travelers’ routes in order to find out if they had been in a risk area neglected the fact that infection could happen en route, that is, in aircrafts and airport transit zones, where people with different itineraries mixed. Pondering the epidemiological implications of transit zones in the 1960s, German health officials noted the oddity of having highly frequented spaces in which passengers and crews from all over the world come together and are “subject to less surveillance than travelers who have been in an outbreak area, but who may not have had any contact with infected persons.”19 There seemed to be no good way out. Even if transit zones were somehow spatially separated into different rooms, “travelers of all origins meet each other again in the airplanes,” German health experts realized. Complicating transit procedures would also have added “increasing time pressure as airspeed increases.” 20 Besides, such procedures would have contradicted the very purpose of airport transit zones, which, according to UN conventions, were supposed to afford the economic benefits of unhindered traffic. Such mobility depended on spaces were people in transit could remain exempt from national controls.
It is telling that the specter of smallpox was ultimately defeated not by restricting global mobilities but by targeting the immobile rest, so to speak, that is, populations in endemic regions. When the WHO announced a plan for the worldwide eradication of smallpox through vaccination in 1967, about sixty percent of the world population lived in endemic countries.21 The project is still widely regarded as the WHO’s biggest achievement. Behind the campaign’s broad humanitarian thrust, however, lay considerable self-interest on the part of the countries in the global North. For European health officials, worldwide vaccination offered an answer to the epidemiological unruliness of air traffic in the context of political unwillingness to impede global commercial traffic. The Health Committee of the Council of Europe concluded in 1962 that even strict controls at airports could not completely prevent the introduction of smallpox and thus argued that the WHO should promote the disease’s global eradication.22 Leading from international air traffic to global vaccination, the case of smallpox thus offers a vivid example of the “relation between mobility and immobility” that interests mobility studies.23
The old idea that borders could work as national disease barriers failed drastically in the case of international airports. In West Germany, it only took one larger viral problem in air traffic for health experts to realize this. Although both the smallpox virus and the vaccine were known, anti-epidemic strategies for airports—like epidemiology in general—had to reckon with several unknowns. One was the obscure itineraries and transits that health experts and officials became increasingly aware of in the early 1960s. Whereas contact tracing in general had already been a pillar of anti-epidemic policies since much earlier in the twentieth century, it was only when health experts tried to develop systematic, in situ control practices that they came to grasp the full extent of this now known unknown in regard to air travel. The cross-linked spatiality of this form of transport combined with its speed and frequency had produced a global network of economically valuable, crisscrossing mobilities that defied the idea of airports as national cordons sanitaires.
It seems clear that knowledge is an important category for scholars working on air mobility, but what does this brief exploration of epidemic control in the early jet age have to say to the history of knowledge more generally? First, I think, it underlines the need to complicate the relation between knowledge and not knowing. It illustrates that gaining knowledge about the existence of unknowns (the making of known unknowns, we might say) is an important part of science and expert practice.24 Second, it suggests the exciting potential of linking the history of knowledge to global history. Integrating knowledge perspectives into our questions and analysis in this case, for example, helps to explain how the growing complexity of the worldwide air transportation network became a challenge for health authorities seeking to control mobility flows at certain hubs within the network. The unintended consequences of this and other global traffic networks and infrastructure, especially the new unknowns they generated, seem particularly relevant in the midst the current global pandemic.
Carolin Liebisch-Gümüş is a research fellow at the German Historical Institute Washington DC. Her current postdoc project is entitled History in Limbo: Airport Transit Zones between Global Mobility and Local Order, 1945–2000.
I would like to thank Mark Stoneman for his close work on previous versions of this article and for challenging me to think about “known and unknown unknowns.”
- Hessisches Hauptstaatsarchiv, 937 130, Walter Gaber, Grundlagenpapier “Pandemie,” November 22, 2006. ↩︎
- For a start, see Lucy Budd, Morag Bell, and Tim Brown, “Of Plagues, Planes and Politics. Controlling the Global Spread of Infectious Diseases by Air,” Political Geography 28, no. 7 (2009): 426–35, PMID: 32288366. ↩︎
- Andrew J. Tatem, “Modern Day Population, Pathogen and Pest Dispersals,” in Human Dispersal and Species Movement. From Prehistory to the Present, ed. Nicole Boicin, Rémy Crassard, and Michael Petraglia (Cambridge, UK: Cambridge University Press, 2017): 521–34. ↩︎
- Harold Edward Whittingham, “Preventive medicine in relation to aviation,” Proceedings of the Royal Society of Medicine 32 (1938): 457. ↩︎
- Institut für Stadtgeschichte Frankfurt, Stadtgesundheitsamt, Sachakten 144, A. Herrlich, “Die Pocken und unserer heutiger Impfschutz,” 1965. ↩︎
- Mark Harrison, Contagion: How Commerce has Spread Disease (New Haven, CT: Yale University Press, 2013). ↩︎
- World Health Organization, International Sanitary Regulations: Proceedings of the Special Committee and of the Fourth World Health Assembly on WHO Regulations No. 2 (Geneva, 1952), 2, https://apps.who.int/iris/handle/10665/85636. ↩︎
- David A. Koplow, Smallpox: The Fight to Eradicate a Global Scourge (Berkeley, CA: University of California Press, 2003), 21. ↩︎
- “Meist Fehldiagnose,” Der Spiegel, March 14, 1962. ↩︎
- Thomas M. Mack, “Smallpox in Europe, 1950–1971,” The Journal of Infectious Diseases 125, no. 2 (1972): 161–69. ↩︎
- Bundesarchiv Koblenz (hereafter: BArch), B142/39, Instructions for airport doctors, draft, November 17, 1960. ↩︎
- BArch, B142/39, Instructions for airport doctors, draft from January 6, 1960. ↩︎
- Malte Thießen, Immunisierte Gesellschaft: Impfen in Deutschland im 19. und 20. Jahrhundert (Göttingen, 2017), 238–40. ↩︎
- BArch, B208/921, Public Health Office Hamburg to Federal Health Office, letter June 26, 1962; Staatsarchiv Hamburg (hereafter: STAHH), 352-6 870, internal letter, November 22, 1962. ↩︎
- STAHH, 352-6 870, Ministry of Interior Baden-Wurttemberg to Federal Health Minister and Public Health Office Hamburg, letter, March 8, 1962. ↩︎
- BArch, B208/921, Health control of sea and air transport, protocol of the Paris meeting of European experts, ca. 1962. ↩︎
- STAHH, 352-6 870, letters involving various federal and state levels from March 8, April 3, and May 14, 1962. ↩︎
- BArch, B208/921, Federal Health Office, report, September 15, 1969; B208/921, Federal Health Office to all state health offices, telex, January 5, 1962; B142/39, minutes of a meeting on instructions for airport doctors, October 13, 1960. ↩︎
- BArch, B208/921, Public Health Office Hamburg to Federal Health Office, letter, June 29, 1961. ↩︎
- STAHH, 352-6 870, internal letter, September 30, 1964. ↩︎
- Koplow, Smallpox, 21 ↩︎
- STAHH, 352-6 870, Federal Minister of Health to the president of the Federal Health Office and all state health offices, letter, August 14, 1962; BArch, B208/921, Health control of sea and air transport, protocol of the Paris meeting of European experts, ca. 1962. ↩︎
- Peter Adey, Mobility (New York: Routledge, 2010), 18. ↩︎
- The notion of “known and unknown unknowns” is used by some scientists, e.g., Rolf H. H. Groenwold, “Commentary: Quantifying the Unknown Unknowns,” International Journal of Epidemiology 49, no. 5 (2020):1503–5. ↩︎