Welcome to this website.  I created this site to make my articles available to other Independent Scholars.  I hope to add other materials relevant to the history of contagionism and contagious diseases.

The picture is a detail of a portrait by William Hogarth thought to be of his friend Dr. John Fothergill.  As a member of the Society of Friends, Fothergill refused to sit for his portrait, so Hogarth probably painted him from memory.

Margaret DeLacy                                                                                                        11/07/2022




Prison Reform in Lancashire, 1700-1850: A Study in County Administration, Stanford University Press: 1986 (now out of print, used copies from Amazon)

The Germ of an Idea: Contagionism, Religion and Society, 1660-1730, Palgrave Macmillan: 2016

Contagionism Catches On: Medical Ideology in Britain, 1730-1800, Palgrave Macmillan: 2017





Unpublished papers/data


Benjamin Franklin and eighteenth-century contagionism

English Religious Laws passed between 1660 and 1728

Timeline of policies/admissions of fellows to the London College of Physicians, 1658-1800

Contagion and the Royal Society, 1657-1723 (data for a paper given to the American Association for the History of Medicine)

Contagion in Manchester (24th International Congress of History of Science, Technology and Medicine (iCHSTM 2013), Manchester, UK 21-28 July 2013

Preventing Contagion: Advice to the Poor (excerpts from John Ferriar of Manchester, John Clark of Newcastle, the Rev. William Clerke of Bury and Francis Barker, of Waterford)


Published papers and articles


Nosology, Mortality and Disease Theory in the Eighteenth Century

Influenza Research and the Medical Profession in Eighteenth Century Britain

The Conceptualization of Influenza in Eighteenth-Century Britain: Specificity and Contagion

Puerperal Fever in Eighteenth-Century Britain



Google NGram of the word "Contagion"


The first peak shown on this graph, in the 1650s appears to be dominated by the metaphoric use of contagion (e.g. the contagion of sin, the contagion of heresies) and to reflect an increase in religious and political tracts during the Interregnum; the second peak, about 1800, is due to medical controversies over whether acute diseases such as jail fever were contagious.



Primary works

These works used to be available online through Google books.  Unfortunately, some of them have been taken offline.     

Anon. A New Discovery of the Nature of the Plague . . . Contrary to the Opinion of Dr. Meade, [sic] Dr. Browne, and others, who give for the First Causes of the Plague . . . Air, Diet, and Disease

(London: T. Bickerton and J. Wilford, n.d. preface dated Aug. 31, 1721

This very rare book is not, strictly speaking, a  contagionist work. It attributed plague to "a subtle active poisonous Body or Insect, very minute ... living on and subsisting by the virulent Matter in the body ... the Air being no more to it, than it is to Birds.  The author, who frequently refers to the similar views of Richard Bradley, suggests that the smaller insects are, the faster they multiply, explaining why plague kills its victims so quickly.  He points out that inanimate particles can't move of their own accord and they become weakened, not increased in power, when they impart their qualities to another body.  Despite Mead's theory that the plague consisted of small venomous particles, bodies could not absorb particles through the pores in the skin because the body constantly exhales through them.  The fact that no epidemic had taken place in England for more than half a century despite many earthquakes, floods, storms, sieges and bad weather showed that these events did not cause the plague.  Similarly, there were many starving and sick people who did not contract plague.  In the second portion of this book, as if he had completely forgotten the argument he had just made, the author blames the bad air emanating from large, closely packed groups of people.  He suggested that the existence of many prison galleys in Marseilles led to the epidemic there and suggested that the largest source for the problem in London was the presence of many prisons within the city.  He called for the removal of criminals to prisons outside the city and for the release of debtors from debtors' prison. The vehemence of his discussion of the plight of London debtors suggests that this advice may have been self-interested, but it was probably sound advice nevertheless.


M.A.C.D. [?Robert Boyle] Systême d'un Medicin Anglois sur la Cause de Toutes Les Especes de Maladies, Avec Les Surprenantes Configurations Des differentes especes de petits Insectes, qu'on voit par le moyen d'un bon Microscope dan le Sang & dan les Urines des differens Malades, & même de tous ceux qui doivent le devenir Recueilli par M.A.C.D.  (Paris:  Alexis-Xavier-Rene Mesnier, 1726)

"The system of an English Doctor on the cause of all sorts of diseases with the surprising appearances of different species of small Insects, which can be seen by the means of a good Microscope in the Blood and in the Urine of different patients, and also in all those who will become ill"

This entertaining treatise, reported to be by a quack physician and juggler called Robert Boyle, Boile or Boil, claims to be a translation of the third part of a treatise entitled "Systems of an English Doctor, on the nature of God & of Souls, on the Generation of every thing, on the cause of all sorts of Maladies, and on their cure, collected and made intelligible... to everyone".  The author explains that he has only translated the third part because the first part (on the nature of God) would be contrary to the revealed truth of our religion, the second (on generation) would wound the modesty of the chaste, and the fourth (on medicine) would not only make all men their own doctors but also all women. 

The Google version, which is digitized from a copy in the University of Lausanne (2009) includes a sequel, "Suite du Systeme d'un Medicine Anglois, sur la Guerison des Maladies, par lequel sont indiquees les especes de Vegetaux & Mineraux, qui sont des Poisons infallibles pour tuer les differentes especes de petits Animaux, qui causent nos Maladies, Recueilli par M.A.C.D. (Paris, Mesnier: 1727)

"The sequel of the System of an English Doctor on the Cure of Illnesses, by which is indicated the sorts of Vegetables and Minerals which are unfailing poisons for kill the different species of small Animals which cause our diseases".

This attributes the earlier work to conversations the author had had with an English doctor, coming from Ispaham (Isfahan) who had been passing through Europe with the Persian Ambassador in 1715.

For the story of this work, see William Bulloch, History of Bacteriology (1938, Dover edn, New York: 1979), p. 32.

William Godwin, DiaryA splendid new annotated online edition of Godwin's diary from the Bodleian Library.


E. H. Griffith, "The Germ Theory"   Griffith reported that, as Charles Singer would later do, he was browsing in an antiquarian shop (this one was in Pike's Peak) when he stumbled on a copy of Marten's work and was transfixed.  This article, from the American Microscopical Journal of 1891, was reprinted twice in other local medical publications, one in St. Louis and the other in Michigan.  The author was presumably Ezra Hollace Griffith, a microscopist, inventor of the "Griffith Stand" and frequent contributor to the journal. Griffith wrote that "The germ theory of disease is generally supposed to be new, and I do not now recall any one who knows it was advocated prior to 25 years ago [i.e. c. 1865]." 


This is a good example of one of those recurrent waves of collective amnesia that often overtook the medical profession.


Benjamin Marten, A New Theory of Consumptions, More especially of a Phthisis or Consumption of the Lungs (London: 1720)The first complete account of Contagium Vivum by an English authorThe first edition appeared in 1720; a second ed. appeared in 1722.


Richard Mead, A Short Discourse Concerning Pestilential Contagion and the Methods to be Used to Prevent it London: Printed for Sam. Buckley in Amen-Corner and Ralph Smith at the Royal-Exchange, 1720.

There were nine editions; the last was in 1744.  The book is dedicated to James Craggs, Secretary of State, who would soon become implicated in the scandal over the bursting of the South Sea Bubble.  Craggs lost his son to smallpox in  February, 1721 and died one month later of a stroke.


For more on this work, see Charles-Edward Amory Winslow, The Conquest of Epidemic Disease (Princeton, 1943) and Arnold Zuckerman, "Plague and contagionism in eighteenth-century England: the role of Richard Mead", Bulletin of the History of  Medicine 2004 Summer;78(2):273-308.



Proceedings of the Board of Health in Manchester (Manchester: Printed by S. Russell for Cadell and Davis ca. 1805)

 This interesting title, now on the Open Collections program on Contagion from the Countway Library at Harvard is accessible from an extremely annoying, slow and balky page viewer. If you can, download a .pdf and read from that. They should let Google Books provide it.




Classic Secondary Works


H[ector] Grasset, "La théorie parasitaire et la phthisie pulmonaire au XVIIIe Siècle", France Médicale (Nov. 17, 1899), translated by Thomas C. Minor as "The Parasitic Theory and Pulmonary Phthisis in the Eighteenth Century" Cincinnati Lancet-Clinic,  n.s. 44 93: (Jan. 6, 1900), 22-26  and (Jan. 13, 1900), 43.

This is very helpful historical review of eighteenth-century contagionist works. Unfortunately, several proper nouns are misspelled in the Minor translation, making it harder to find the article through Google searches.  As far as I know, 20th. century historians were unaware of this article. I have not been able to locate the original French, version.



William MacMichael, "A Brief Sketch of the Progress of Opinion on the Subject of Contagion; with some Remarks on Quarantine"


The URL points to the text provided by the Harvard University Library website for "Contagion: Historical Views of Diseases and Epidemics".  This copy, which begins on p. 519 of an unnamed source (perhaps The Pamphleteer) appears to be the same as a work listed by Google Books as being published in London by John Murray in 1826, but the Google link does not provide a text.  MacMichael wrote this work in an effort to refute the arguments of Charles MacLean who had called for an end to quarantines against Plague.  In this short work MacMichael analyzes the views of several British authors about the contagiousness of several febrile diseases including smallpox and scarlet fever. 








Classic Articles


Other Diseases



Classic articles


Charles Singer, "Notes on the Early History of Microscopy" Proceedings of the Royal Society of Medicine (1914) (Section of the History of Medicine) 7: 247–279. PMCID: PMC2003539

A rare full-text public-access copy of one of Singer's early articles courtesy of PubMed 







Achtman, Mark, Morelli, Giovanna, Zhu Peixuan et. al. "Microevolution and history of the plague bacillus, Yersinia pestis" Proc. National Academy of Sciences, U.S. A., December 21, 2004;

101(51): 17837–17842. Published online 2004 December 14. doi: 10.1073/pnas.0408026101


Ayyadurai S, Sebbane F, Raoult D, Drancourt M. "Body lice, Yersinia pestis Orientalis, and Black Death" [letter]. Emerg Infect Dis [serial on the Internet]. May, 2010 .

"Paleomicrobiology suggested that most historical cases in Europe resulted from Orientalis....Our data support an alternative scenario of the historical plague epidemics transmitted by body lice, with Orientalis being the only such louse-borne transmissible biotype."


Dean, Katharine, Fabienne Krauer, Lars Walloe et. al., 

"Human ectoparasites and the spread of plague in Europe during the Second Pandemic"
Proceedings of the National Academy of Sciences, January 2018 115(6):201715640
DOI: 10.1073/pnas.1715640115

Historians try to avoid reading present knowledge back into the past, but it is difficult to accomplish completely.  Although some historians have noted that early modern land-based quarantines sometimes appeared to circumscribe plague epidemics, others have assumed that they would have been ineffective because the rats that carried the plague cannot be contained by a quarantine.  A few have also claimed that past accounts of pestilence cannot have represented experiences with true "bubonic" plague--y. pestis--because the epidemiology did not match the known prevalence of rats.  Following up on the suggestion in a letter by Ayyadurai et. al., (see above) Dean at el. have conducted an epidemiological study of 9 outbreaks and conclude that bubonic plague, in addition to pneumonic plague, might have spread primarily through human ectoparasites--that is, by human fleas and lice:


"we demonstrate that human ectoparasites appear to have been the dominant transmission mode for plague during the Second Pandemic. This alternative mode of transmission could account for many of the epidemio-

logical differences between the Second Pandemic and those caused by rats during the Third Pandemic."



Stephanie Haensch, Raffaella Bianucci, Michel Signoli, et. al, "Distinct Clones of Yersinia pestis Caused the Black Death" Oct 7, 2010 PLoS Pathog 6(10): e1001134. doi:10.1371/journal.ppat.1001134


For about the past decade, there has been a fierce debate about whether the "third pandemic" of Plague (Yersinia pestis) that broke out during the 19th. century was caused by the same agent as the earlier pandemics known as the Plague of Justinian and the Black Death. DNA analysis of cells recovered from medieval graveyards yielded some evidence that this was the case.  However, the evidence did not convince all doubters.  Some skeptics argued that the earlier pandemics did not conform to the pattern that would be found in a disease carried by rats and rat fleas and suggested that the DNA analysis had used samples contaminated in the lab.  Others argued that the epidemiology of the Black Death suggested a disease that spreads by contagion from person to person not one transmitted by rats and their fleas.  For example, the Black Death appeared in Iceland which does not have rats, and in other places that were considered too cold to sustain an epidemic of Plague.  These three articles appear to resolve the issue.  They identify two variants of Yersinia pestis as the agent of the second pandemic (1348-1750) and suggest a possible additional mechanism of transmission in the form of human lice.  Lice are also the main vectors of typhus.



Runfola, Janine, et. al."Outbreak of Human Pneumonic Plague with Dog-to-Human and Possible Human-to-Human Transmission — Colorado, June–July 2014" May 1, 2015 / 64(16);429-434 from the Centers for Disease Control, Morbidity and Mortality Weekly Report

"Pneumonic plague occurs as either a complication of untreated bubonic plague (10%–13% of all cases) or as a primary pneumonia following inhalation of infectious droplets (2% of all cases) (4). Untreated pneumonic plague has a fatality rate of ≥93% and can be spread from person to person through aerosols generated during coughing. . . .  In this outbreak, all four patients had laboratory-confirmed plague, including three patients (A, B, and D) with clinical and radiographic evidence of pneumonia. . . .This outbreak began with illness in a pet dog, a previously unrecognized source of plague exposure in the United States. The only previously published case of direct transmission of plague from a dog to a human was reported from China in 2009."



Verena J. Schuenemann, Kirsten Bos, Sharon DeWitte et al. Targeted enrichment of ancient pathogens yielding the pPCP1 plasmid of Yersinia pestis from victims of the Black Death  Approved July 22, 201, PNAS August 29, 2011 1

Genetic testing of over 100 skeletal remains in a London plague graveyard yielded evidence of a previously unknown variant of Y. pestis.



Maria Spyrou, Rezeda I. Tukhbatova, Chuan-chao Wang and others "Analysis of 3800-year-old Yersinia pestis genomes suggests Bronze Age origin for bubonic plague" Nature Communications, June 8, 2018

From the abstract: "Although the earliest evidence of Y. pestis infections in humans has been identified in Late Neolithic/Bronze Age Eurasia (LNBA 5000–3500y BP), these strains lack key genetic components required for flea adaptation, thus making their mode of transmission and disease presentation in humans unclear. Here, we reconstruct ancient Y. pestis genomes from individuals associated with the Late Bronze Age period (~3800 BP) in the Samara region of modern-day Russia. We show clear distinctions between our new strains and the LNBA lineage, and suggest that the full ability for flea-mediated transmission causing bubonic plague evolved more than 1000 years earlier than previously suggested. Finally, we propose that several Y. pestis lineages were established during the Bronze Age, some of which persist to the present day."

This article is summarized for lay readers in Kiona N. Smith, "4,000-year-old genomes point to origins of bubonic plague" Ars Technica, June 12, 2018:



Other diseases


David M. Morens, Jeffery K. Taubenberger, Gregory K. Folkers, and Anthony S. Fauci, "Pandemic Influenza's 500th. Anniversary," Clinical Infectious Diseases Dec. 15, 2010, vol. 51(12), 1442-44,  doi: 10.1086/657429 PMCID: PMC3106245 PMID: 21067353


Jing Yana, Michael Granthama, Jovan Pantelica, P. Jacob Bueno de Mesquitaa, Barbara Alberta, Fengjie Liua, Sheryl Ehrmanb, Donald K. Miltona, EMIT Consortium, "Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community. PNAS, approved December 15, 2017. doi 10.1073/pnas.1716561115

    Eighteenth-century authors believed that contagion was transmitted by breathing; a contention later dismissed by researchers who affirmed the germ theory of contagion, the role of droplet infection and the importance of handwashing.  Now, it appears the earlier authors may have been correct, at least in the case of influenza:

"We provide overwhelming evidence that humans generate infectious aerosols and quantitative data to improve mathematical models of transmission and public health interventions. We show that sneezing is rare and not important for—and that coughing is not required for—influenza virus aerosolization"

Max Planck Institute for the Science of Human History. "Possible cause of early colonial-era Mexican epidemic identified: Salmonella enterica, the bacterium responsible for enteric fever, may be the long-debated cause of the 1545-1550 AD 'cocoliztli' epidemic in Oaxaca, Mexico, that heavily affected the native population." ScienceDaily. (accessed September 6, 2018).

Zhou et al. Pan-genome Analysis of Ancient and Modern Salmonella enterica Demonstrates Genomic Stability of the Invasive Para C Lineage for Millennia. Current Biology, 2018 DOI: 10.1016/j.cub.2018.05.058

    This article describes the genetic analysis of a bacterium found in the skeleton of a young woman buried in Trondheim, Norway who died between 1150 and 1250 C.E.  The research team at Warwick university, led by Mark Achtman, concluded that she died of enteric fever. They concluded that this pathogen evolved in Europe and was also responsible for the pestilence in Mexico in 1545.


This article is summarized for lay readers in University of Warwick, "Evidence of Salmonella Paratyphi C found for the first time in medieval northern Europe: Eight hundred year old Norwegian skeleton found to have traces of Salmonella."








    The Age of Revolutions: A cooperative blog providing essays on the cultural history of the idea of revolution.

    Alun Withey's blog maintained by Alun Withey, a historian of medicine, culture and the body in the eighteenth century.    

    "Applying new Methods with GIS/Space-time/behavior in medical Geography" one of many fascinating sets of webpages by Brian Altonen.  See also his Pinterest board of historical disease maps

    Art UK: huge searchable collection of images from British collections contributed by more than 3,000 institutions

    "Black Death" page on medievalists. net

   "Books, Health and History" from the New York Academy of Medicine

    "British Libary blogs" a collection of blogs by members of the British Library staff focusing on British Library collections

    "Celebrating Jewish Archives" Guide to a consortium of Jewish Archives in Britain

    Connected Histories service that conducts simultaneous search through more than two dozen digital history databases and archives covering British history 1500-1900.  Can be frustrating, especially for non-UK citizens, when results point to paywalled archives (such as Gale collections) but amazingly efficient at searching.

    Contagion: Historical Views of Diseases and Epidemics From Harvard University, a selection of open-source texts.  Gives relatively little attention to eighteenth-century British works

    Contagions blog by Michelle Ziegler

    The Cullen Project The Consultation Letters of Dr William Cullen (1710-1790) at the Royal College of Physicians of Edinburgh.

    Dalhousie University, History of Medicine Resources comprehensive list of major medical resources

    Digital Collections from the National Library of Medicine. Repository of public domain materials in biomedical history

    Dissenting Academies: a list on the website "Technical Education Matters" created by Dr. Richard Evans

    Early Modern History Resources from MEMSLib at the University of Kent

    Early Modern Online Bibliography a blog developed by Anna Battigelli (SUNY Plattsburgh) and Eleanor Shevlin (West Chester University of Pennsylvania) to facilitate scholarly feedback and discussion pertaining to text databases for the humanities, such as EEBO, ECCO, and the Burney Collection.

    Early Modern Practitioners a database in progress with biographies of medical practitioners in England, Wales and Ireland, c.1500-1715 hosted  by the Centre for Medical History (CHM) at Exeter University

    Early Modern Online Recipes Collection (EMROC) a project to recover, transcribe, and analyse early modern recipe books, many containing medical recipes and/or advice

    Eighteenth Century Common a website providing discussions  by eighteenth-century scholars about their work, targeted for the general reader.  

    The Galileo Project: Catalog of the Scientific Community in the 16th. and 17th. Centuries compiled by Richard S. Westfall

    History of the Health Sciences World Wide Web Links compiled by Patricia E. Gallagher and Stephen J. Greenberg, a comprehensive listing of major medical history web resources including blogs, journals, biographies of individuals, and sites for particular diseases

    History of Medicine in Ireland blog: A collection of short articles and events hosted by the Centre for the History of Medicine in Ireland, University College Dublin and the Royal College of Physicians of Ireland Heritage Centre.

    Hyde Collection Catablog: Provided by the Houghton Library at Harvard University, this blog centers on the Hyde Collection of material on Samuel Johnson.

    Infectious Diseases: an online exhibit by the Edward Worth Library in Dublin.  Includes sections for Plague, Smallpox, Syphilis, Tuberculosis, Fevers and Theory of Contagion with a well-researched text.

    Isis Current Bibliography Eplore.  Citations and more for works in the history of Science, Medicine and Technology in this compilation of the Isis Current Bibliography. The Isis Cumulative Bibliography, 1913-1975 will eventually be merged with this database.

    John Rylands Library Special Collections blog  Posts by Karen Rushton discuss a variety of eighteenth- and nineteenth-century medical topics that are illuminated by holdings in the John Rylands library in Manchester including botany, midwifery, and Manchester doctors.  See also the John Rylands Research Institute medical collections website which states that the collections include twenty separate medical archives.


    Map of Early Modern London (MoEML) Blog and website including an interactive map and gazetteer that explore the use of GIS data to uncoverthe meaning and representation of cultural and geographic space in the London of Shakespeare and his contemporaries.


    Medical Heritage Library a digital library of works in the history of medicine curated by a consortium

of large research libraries including the National Library of Medicine

    Medical Humanities Dissertations: Compiled by John Erlen of the University of Pittsburgh, monthly listings of dissertations classified by topic.

    Medical Humanities and Medical History Blogs: Large Compilation from McMaster University

    MedPlag: Medieval Plagues: Ecology, Transmission Modalities and Routes of the Infections: research project website

    Publishing the Philosophical Transactions: a project and accompanying blog housed at the University of St. Andrews on the economic, social and cultural history of the Philosophical Transactions of the Royal Society.

    Oregon Rare Books Initiative a blog from the Rare Books collection of the Knight Library at the University of Oregon including scheduled lectures.

    Othemeralia: Blog from the Othmer Library of Chemical History at the Chemical Heritage Foundation in Pennsylvania

    Quarantine Studies: This is a Wordpress blog for a group of scholars interested in the history of Quarantines and Lazarettos.  Their focus seems to be the Mediterranean.   They have created an associated list of reference materials on Zotero . 

    Pandemics in Historical Perspective:  A Bibliography for Evaluating the Impacts of Diseases Past and Present by Hannah Johnston, NYAM Library Volunteer, June 2020.  Annotated bibliography of works published between 2000 and 2020.

    The Recipes Project: website and associated media devoted to studying the meaning and use of recipes in Food, Magic,  Science, Art and Medicine

    Remedia: a history of medicine blog from Harvard University

    The Repository: the History of Science blog of the Royal Society

    Shells and Pebbles: a History of Science blog from the Netherlands

    Six Degrees of Francis Bacon Created by teams at Georgetown and Carnegie Mellon, this innovative project maps and displays early modern social networks.  The inital diagrams were based on the Oxford Dictionary of National Biography but the interface supports crowdsourcing, so the amount of information should grow substantially.

    The Sloane Letters Blog maintained by historian Lisa Smith at the University of Saskatchewan

    Vesalius journal published by the International Society for the History of Medicine (ISHM): all issues except the most recent are available via open access online.

    The Voltaire Foundation Blog cooperative blog on Voltaire and the Enlightenment, strongest in French history and culture.

    Wellcome Library Blog  The blog includes a "blogroll" listing many other health and medicine blogs

    "'Where Mis'ry Moans:' Four Prison Reformers in Eighteenth & Nineteenth Century England"  An online exhibit by the Harvard Law School Library spotlights my earlier book, Prison Reform in Lancashire which also  includes a discussion of the late eighteenth-century typhus epidemic.






Several medical libraries and history of medicine institutions host history of medicine lectures periodically.  They have begun to make these available as podcasts or streaming audio/video recordings.  The technical quality is often poor--amounting to a recorder near the dais in a large auditorium when the lecture is given, but the lectures themselves are often wonderful.  I don't know of any source that catalogs/indexes these by speaker or subject or even of any master list of these lectures but here are links to a few libraries that have announced the availability of audio/video records of this sort of event


"Coughs, Sneezes, and Jet-propelled Germs," courtesy of the Public Domain Review and the Internet Archive, here are two (very) short films on using and cleansing handkerchiefs created by Richard Massingham (1898–1953), a former Senior Medical Officer at the London Fever Hospital who also stars in each one.


Images from the Wellcome Library


Medical History "Highlights of a Decade": reflections by authors of Medical History articles


National Library of Medicine History Talks


Oregon Health and Science University, Historical Collections and Archives lecture series


Owsei Temkin on Galenism and Galenics in the History of Medicine

 a radio talk "for Doctors Only" broadcast by WNYC in 1957


Oxford Brookes University, "Moments in Medicine"  


Reynolds Historical Library, University of Alabama lecture series




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