Stowaway Mosquitoes and Twentieth-century Quarantine Knowledge 

In July 1906, a Connecticut newspaper published a short note about yellow fever concerns in Texas¹. State health officer Dr. Tabor pleaded with the public to help keep the dreaded disease at bay: “Now is the time for every citizen to do his duty. Get your people interested. Don’t read this and throw it aside. Remember what one single case of yellow fever means to a Texas city or town.” His warning referred not only to the disease itself, which had repeatedly infested the state throughout the 1800s. It also alluded to the hardships of quarantine, which would have disrupted any trade connections to and from affected areas. The health officer proposed a solution, condensed to a simple formula: “[N]o mosquitoes, no yellow fever, no quarantine.” 

Around 1900, the Reed Commission, tasked with studying yellow fever in US-occupied Cuba, had proven that the disease is transmitted by Aedes aegypti mosquitoes. This discovery fundamentally changed yellow fever control: Targeting and eliminating mosquitoes and their breeding grounds turned out to be an effective tool against outbreaks.² Havana was soon declared free of yellow fever; cities and regions all over the Americas followed in the next decades. This story illustrates changes in quarantine knowledge and regulations in the twentieth century: Quarantine – at state and national borders, between and within communities – had been the main defense against yellow fever and other infectious diseases for centuries. It had engendered its own complex system of knowledge, experts, and technologies. With the advent of bacteriology, new insights about disease vectors, and the availability of a growing number of vaccines, quarantine came to be seen as a thing of the past. Quarantine and “modern” knowledge appeared to be almost polar opposites: The new medical knowledge shortened, limited, and, at best, obliterated the burden of quarantine. If we follow this logic, thinking about mosquitoes and infectious disease leads us away from the history of quarantine knowledge into an age governed by the logic of eradication and vaccines. 

I want to suggest that the opposite is true: Thinking about mosquitoes can help us uncover hidden forms and overlooked manifestations of quarantine knowledge. Quarantine ceased to play an active part in the lives of many people in the course of the twentieth century. But it was never really gone – a fact underscored by the Covid-19 pandemic. Its form, locations, and targets shifted, but it continued to influence the ways in which we perceive, govern, and inhabit space. It was also continuously intertwined with ideologies and racist practices. If we want to understand what quarantine meant during the twentieth century and how its relationship with “modern” medical knowledge developed, we can find excellent starting points by following the lead of the mosquitoes.

Applying Dr. Tabor’s formula – “no mosquitoes, no yellow fever, no quarantine” – proved to be more difficult than expected. While mosquito eradication worked on a local level, the increasing interconnectedness of world regions posed some (familiar) problems: “A steamer with sickness aboard can be quarantined; but who can quarantine mosquitoes?,” lamented the Hawaiian Pacific Commercial Advertiser in 1909.³ Indeed, stowaway mosquitoes, “hiding” on ships, trains, and especially in airplanes, became one of the specters of infectious disease control in the twentieth century.⁴ They made their way into international quarantine agreements, shaping the spaces and physical environment surrounding us in very concrete ways: The International Sanitary Convention of 1926 specified that “[r]ailway cars running in countries where yellow fever exists must be so arranged as to be as little suited as possible for the transport of Stegomyia”⁵(another name for the mosquito that transmits the disease). From the 1930s, “anti-amaryl aerodromes” were built with the idea of creating safe, mosquito-free travel hubs in endemic areas.⁶ In 1971, WHO officials traveled around the world with cages containing mosquitoes in order to determine the efficiency of disinsection routines: The cages were placed in hidden corners of airplanes; after disinsection, the experts checked whether the procedure, which bombarded the mosquitoes with insecticide, had worked, or whether the mosquitos had survived.⁷

These glimpses hint at a revised system of quarantine targeting mosquitoes rather than humans: The “disinsection” measures employed in trains, airplanes, or at airports aimed at keeping infected and non-infected mosquito populations apart. The roots of this thinking can be traced back to the early 1900s, when concerns about yellow fever spreading to Asia surfaced: India and other countries around the Indian Ocean had not previously been affected by the disease but hosted large populations of Aedes aegypti and were, therefore, considered to be at risk of importing the virus.⁸ After 1930, spurred on by the rise in air traffic, a new geography of yellow fever materialized: Virologists, epidemiologists, and entomologists worked together on the project of mapping “endemic” and “receptive” yellow fever areas.⁹ These maps formed the basis for subsequent yellow fever quarantine agreements. This was not entirely new: Quarantine has always entailed the separation of “infected” and “clean” spaces. But the mapping of yellow fever areas is an example for an important change in the logic of quarantine in the twentieth century: The risk status of spaces was, at least partially, uncoupled from outbreaks. Yellow fever endemicity did not necessarily mean that there were visible epidemics or even recognized clinical cases among humans.¹⁰ It merely referred to the presence of the virus – established, for example, through immunity tests – as well as suitable mosquito vectors. Similarly, not all receptive areas had experience with previous outbreaks. In some of the countries now considered most at risk, like India and South Africa, the disease had never caused an outbreak before. The presence of Aedes aegypti mosquitoes and a “favorable climate” were enough to put them on the risk map.

This new landscape of quarantine was not antithetical to “modern” medical knowledge; it came into existence becauseof it. Twentieth-century quarantine knowledge was the result of an increasingly interdisciplinary collaboration of experts who shared a new perspective on space: Mosquitoes, like viruses or bacteria, drew attention to the smallest of spaces and to the (almost) invisible. In order to “quarantine” mosquitoes, one had to locate them first: Considerable energy and resources went into mapping mosquito populations, finding hiding places and potential holes in protective barriers. Making “contamination” visible required new technologies and highly specialized expertise; the absence of illness and death was no longer enough to assume that a place could be considered safe. Beyond the micro-scale of infection, mosquitoes also played an important role in redefining macro-scales: The presence or absence of the disease vectors could divide regions but also foster new alliances and large-scale (trans-)regional cooperation. Following the mosquitoes can help us uncover these new spatial dimensions characteristic of quarantine knowledge in the twentieth century.Like human disease vectors, mosquitoes are constantly on the move and can cover considerable distances. The fact that disease geographies are shaped by human movement has been emphasized many times.¹¹ Animal movement has received less attention. By focusing on this aspect, and by taking non-human travelers seriously as independent actors, we can de-center the history of quarantine knowledge and include a broader environmental perspective. The public debate about the dangers of “stowaway” mosquitoes on airplanes is telling in this regard: On the one hand, it ascribes a sinister quasi-agency to mosquitoes, accusing them of “hiding” from public health authorities. On the other hand, it portrays the movement of mosquitoes as a simple, accidental byproduct of human mobility: If access to ships, trains, and airplanes could be blocked, it argues, then mosquitoes and diseases would stay confined to their “natural” habitats.

The reality was more complex than this debate suggested, as epidemiological entomologists were well aware. Experts in the discipline studied many problems related to mosquito mobility, in connection with, but also independently of, means of human transport. Understanding if and for how long mosquitoes could survive on an airplane, how far they could fly on their own, whether they lived close to humans or also in more remote areas, and where they bred was essential for the development of new, more effective quarantine and mosquito control schemes. Yet, the more the scientists learned about the insects, the more questions arose. In the case of yellow fever, it turned out that not only Aedes aegypti but also several other types of mosquitoes could transmit the disease. In the 1930s, a second cycle of transmission involving forest-dwelling mosquitoes and primates was discovered.¹² Research in Africa showed that mosquitoes of the same species could have regional or even local variations in their biting behavior and relationship to humans.¹³

All of these discoveries pointed towards a growing realization that quelled the hopes of getting rid of mosquitoes (and quarantine) forever: Nature can never be fully controlled. Humans cannot uncouple themselves from their relationships with non-human actors, or, more broadly, with the environment. There is no question that humans have massively shaped the geographies of infectious diseases and their vectors: Deforestation, the intentional introduction of animal species into new habitats, and human-driven global warming, to name just a few examples, have all changed the distribution of disease vectors. These examples also show, however, that the human impact is more complex than simply providing a new form of transport for mosquitoes. Disease geographies are constantly evolving and changing, with and without human influences. The attempt to fully control these geographies by defining fixed risk zones and putting up protective barriers came under increasing scrutiny during the second half of the twentieth century. Quarantine did not disappear from the toolbox of the fight against pandemics. But its shape and relation to other preventive measures changed as strategies of infectious disease management shifted and the concept of preparedness gained importance. Zooming in on mosquitoes is one way to write a history of quarantine knowledge that takes these intricate connections between humans and non-humans into account and allows for a wider, planetary perspective on global health.

Despite this proposed shift towards “mosquito quarantine,” we can – and should – ask if and how this new type of twentieth-century quarantine continued to affect humans directly. In the case of yellow fever, a vaccine has been available since the 1930s and is still mandatory today for those traveling to (potentially) affected areas.¹⁴Vaccinated travelers are exempt from quarantine regulations. At first glance, this system comes very close to ending the burden of quarantine for humans. When we look closer, however, it becomes clear that this has not been true for everyone. For example, while vaccinated airline passengers were increasingly able to travel freely to and from yellow fever areas, some countries executed forceful “relocations” of “native” populations around airports under the guise of creating sanitary buffer zones.¹⁵ Racial segregation as a measure of yellow fever prevention was in use well into the twentieth century.¹⁶ Even today, immunization coverage is distributed unevenly and remains too low, especially in some parts of Africa where epidemics continue to occur regularly.¹⁷ When thinking about the relationship between knowledge and quarantine in the twentieth century, we need to take these examples into account: Quarantine knowledge, like all biomedical knowledge, was never “neutral” but deeply intertwined with other knowledge systems and ideologies, like racism. In addition, “modern” methods of disease control propagated by health officials like Dr. Tabor in Texas required not only knowledge but also money and infrastructures. Presenting knowledge – as well as individual responsibility – as the solution to eliminate quarantine, as Tabor did in the passage cited at the beginning of this article, can distract from the structural inequalities that shaped quarantine throughout the twentieth century. 

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Laura-Elena Keck is a historian and postdoctoral researcher at the University of Leipzig. As a member of the interdisciplinary LeipzigLab and the DFG-funded research project “Pandemic Space: Understanding Quarantine and Responsibilization in Times of Corona”, she is currently working on a transregional history of quarantine knowledge in the 20th century, with a focus on the USA and South Africa. Her research interests include the cultural history of medicine, health, and nutrition, the history of knowledge and the body, and transregional/ transnational approaches to history.

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1. The Daily Morning Journal and Courier (New Haven), July 5, 1906; Chronicling America: Historic American Newspapers, Lib. of Congress[↩]
2. See, for example, Alexandra Minna Stern, “Yellow Fever Crusade: US Colonialism, Tropical Medicine, and the International Politics of Mosquito Control, 1900–1920,” in Medicine at the Border: Disease, Globalization and Security, 1850 to the Present, ed. Alison Bashford, 41–59 (Basingstoke: Palgrave Macmillan, 2007).[↩]
3. The Pacific Commercial Advertiser (Honolulu), May 10, 1909; Chronicling America: Historic American Newspapers, Lib. of Congress[↩]
4. 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.[↩]
5. “Convention Between the United States and Other Powers Revising the International Sanitary Convention of January 17, 1912, Signed at Paris, June 21, 1926”,” Article 60, The Office of the Historian[↩]
6. H. E. Whittingham, “Preventive Medicine in Relation to Aviation,” Proceedings of the Royal Society of Medicine 32, no. 5 (1939): 458–61.[↩]
7. Some of these experiments were documented by photographer Monique Jacot. [↩]
8. Kavita Sivaramakrishnan, “Yellow Fever, Quarantine and the Jet Age in India: Extremely Far, Incredibly Close,” in Quarantine: Local and Global Histories, ed. Alison Bashford, 154-72 (Basingstoke: Palgrave Macmillan, 2016), 158.[↩]
9. Jennifer Tappan, “Wandering Epizootics and Zones of Emergence: Constructing Yellow Fever Endemicity in Africa,” Health & Place 77 (2022): 102770.[↩]
10. This was the case, for example, in Sudan before the Nuba Mountains epidemic of 1940. See Heather Bell, Frontiers of Medicine in the Anglo-Eqyptian Sudan, 1899–1940, Oxford Historical Monographs (Oxford: Clarendon Press, 1999), 163–97.[↩]
11. See, e.g., Mark Harrison, Contagion: How Commerce Has Spread Disease (New Haven: Yale University Press, 2012).[↩]
12. Emilio Quevedo et al., “Knowledge and Power: The Asymmetry of Interests of Colombian and Rockefeller Doctors in the Construction of the Concept of ‘Jungle Yellow Fever,’ 1907–1938,” Canadian Bulletin of Medical History 25, no. 1 (2008): 71–109.[↩]
13. For a discussion of some of the open questions regarding yellow-fever-transmitting mosquitoes, see World Health Organization & Expert Committee on Yellow Fever‎, “Criteria Required for the Delineation of Yellow-Fever Receptive Areas throughout the World” (Geneva: World Health Organization, 1953).[↩]
14. For background information on the history of the yellow-fever vaccine, see John Farley, To Cast Out Disease: A History of the International Health Division of the Rockefeller Foundation (1913–1951) (Oxford: Oxford University Press, 2004), 169–82.[↩]
15. World Health Organization & Expert Committee on Yellow Fever, “Official Documentation Relating to Notifications or Requests Received from Several Governments with a View to the Exclusion or Inclusion of Territories in Yellow-Fever Endemic Zones” (Geneva: World Health Organization, 1953), 17.[↩]
16. Liora Bigon, “Transnational Networks of Administrating Disease and Urban Planning in West Africa: The Inter-Colonial Conference on Yellow Fever, Dakar, 1928,” GeoJournal 79 (2014): 107–109.[↩]
17. Currently, around 90 percent of reported yellow fever cases occur in Africa; see Megan Vaughan, “A Research Enclave in 1940s Nigeria: The Rockefeller Foundation Yellow Fever Research Institute at Yaba, Lagos, 1943–49,” Bulletin of the History of Medicine 92, no. 1 (2018): 203. Since 2005, the WHO and other global health actors have started several initiatives aimed at improving vaccine coverage in Africa; see, e.g., <https://www.who.int/initiatives/eye-strategy> for the most current WHO initiative.[↩]

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