John Snow: Anesthesiologist, Epidemiologist, Scientist, and Hero.

A 19th century physician was crucial to the establishment of 2 medical specialties-anesthesiology and public health. Everyone whose interest in public health has increased in the last year will be amazed at Dr John Snow's career in anesthesiology. Those who recognize him as the first full-time physician anesthetist will be struck by his development of medical mapping during the Cholera Pandemic of 1848, resulting in one of the fundamental techniques of epidemiology and public health that has continued through today. Snow's accomplishments in anesthesiology and epidemiology reflected a concatenation of science, focus, and creativity. His training in the early 19th century integrated science, medicine, and his keen interest in respiratory physiology. His early clinical exposure to colliery workers in Newcastle was likely influenced by the earlier development of pneumatic medicine. He was committed to the notion that chemistry, especially the use of medicinal gases, would be transformative for medicine. Thus, he was "primed" when the news of the American anodyne ether reached London in 1846. When the third cholera pandemic reached London shortly thereafter, in the fall of 1848, his academic and practical understanding of gas chemistry and pharmacology, respiratory physiology, and anesthetic agents led him to question the popularly promulgated miasma-based theories of transmission. His methodical investigations, research, and perseverance were mirrored in his scholarly work, numerous presentations, and public advocacy. He articulated many scientific principles essential to the early practice of anesthesia-anesthetic potency, quantitative dosing of anesthetic agents, engineering principles required for conserving the latent heat of vaporization, and minimizing the contribution of anesthetic equipment to airway resistance. He moved easily and methodically between these worlds of physiology, chemistry, engineering, clinical medicine, and public health. In his role as the first medical epidemiologist, Snow understood the power of medical mapping and the graphic presentation of data. He was a pioneer in 2 nascent fields of medicine that were historically and remain contemporarily connected.

A box, a trough and marbles: How the Reed-Frost epidemic theory shaped epidemiological reasoning in the 20th century.

The article takes the renewed popularity and interest in epidemiological modelling for Covid-19 as a point of departure to ask how modelling has historically shaped epidemiological reasoning. The focus lies on a particular model, developed in the late 1920s through a collaboration of the former field-epidemiologists and medical officer, Wade Hampton Frost, and the biostatistician and population ecologist Lowell Reed. Other than former approaches to epidemic theory in mathematical formula, the Reed-Frost epidemic theory was materialised in a simple mechanical analogue: a box with coloured marbles and a wooden trough. The article reconstructs how the introduction of this mechanical model has reshaped epidemiological reasoning by shifting the field from purely descriptive to analytical practices. It was not incidental that the history of this model coincided with the foundation of epidemiology as an academic discipline, as it valorised and institutionalised new theoretical contributions to the field. Through its versatility, the model shifted the field's focus from mono-causal explanations informed by bacteriology, eugenics or sanitary perspectives towards the systematic consideration of epidemics as a set of interdependent and dynamic variables.

Imagination and remembrance: what role should historical epidemiology play in a world bewitched by mathematical modelling of COVID-19 and other epidemics?

Although every emerging infectious disease occurs in a unique context, the behaviour of previous pandemics offers an insight into the medium- and long-term outcomes of the current threat. Where an informative historical analogue exists, epidemiologists and policymakers should consider how the insights of the past can inform current forecasts and responses.

The Centennial of the Department of Epidemiology at Johns Hopkins Bloomberg School of Public Health: A Century of Epidemiologic Discovery and Education.

The Department of Epidemiology at Johns Hopkins School of Hygiene and Public Health was founded in 1919, with Wade Hampton Frost as inaugural chair. In our Centennial Year, we review how our research and educational programs have changed. Early years focused on doctoral education in epidemiology and some limited undergraduate training for practice. Foundational work on concepts and methods linked to the infectious diseases of the day made major contributions to study designs and analytical methodologies, largely still in use. With the epidemiologic transition from infectious to chronic disease, new methods were developed. The Department of Chronic Diseases merged with the Department of Epidemiology in 1970, under the leadership of Abraham Lilienfeld. Leon Gordis became chair in 1975, and multiple educational tracks were developed. Genetic epidemiology began in 1979, followed by advances in infectious disease epidemiology spurred by the human immunodeficiency virus/acquired immune deficiency syndrome epidemic. Collaborations with the Department of Medicine led to development of the Welch Center for Prevention, Epidemiology, and Clinical Research in 1989. Between 1994 and 2008, the department experienced rapid growth in faculty and students. A new methods curriculum was instituted for upper-level epidemiologic training in 2006. Today's research projects are increasingly collaborative, taking advantage of new technologies and methods of data collection, responding to "big data" analysis challenges. In our second century, the department continues to address issues of disease etiology and epidemiologic practice.

Seventy Years of Tuberculosis Prevention: Efficacy, Effectiveness, Toxicity, Durability, and Duration.

Tuberculosis (TB) has been a leading infectious cause of death worldwide for much of human history, with 1.6 million deaths estimated in 2017. The Department of Epidemiology at the Johns Hopkins Bloomberg School of Public Health has played an important role in understanding and responding to TB, and it has made particularly substantial contributions to prevention of TB with chemoprophylaxis. TB preventive therapy is highly efficacious in the prevention of TB disease, yet it remains underutilized by TB programs worldwide despite strong evidence to support its use in high-risk groups, such as people living with HIV and household contacts, including those under 5 years of age. We review the evidence for TB preventive therapy and discuss the future of TB prevention.

Post-Modern Epidemiology: When Methods Meet Matter.

In the last third of the 20th century, etiological epidemiology within academia in high-income countries shifted its primary concern from attempting to tackle the apparent epidemic of noncommunicable diseases to an increasing focus on developing statistical and causal inference methodologies. This move was mutually constitutive with the failure of applied epidemiology to make major progress, with many of the advances in understanding the causes of noncommunicable diseases coming from outside the discipline, while ironically revealing the infectious origins of several major conditions. Conversely, there were many examples of epidemiologic studies promoting ineffective interventions and little evident attempt to account for such failure. Major advances in concrete understanding of disease etiology have been driven by a willingness to learn about and incorporate into epidemiology developments in biology and cognate data science disciplines. If fundamental epidemiologic principles regarding the rooting of disease risk within populations are retained, recent methodological developments combined with increased biological understanding and data sciences capability should herald a fruitful post-Modern Epidemiology world.

From bacterial genomics to clinical epidemiology: an interview with Bill Hanage.

Bill Hanage is an Associate Professor of Epidemiology at Harvard School of Public Health, where he studies fundamental and applied epidemiology using genomic and evolutionary methods. Bill spoke to us about the different types of selection that determine pathogen populations, asking reviewers to highlight positives of papers, and whether we're closer to a causal framework for studying the microbiome.

Research trends in flavonoids and health.

Herein we describe, based on some bibliometric data, how the field of research on flavonoids has evolved over the last 25 years. The number of papers on flavonoids has risen in an exponential manner over these years, much faster than other fields on food constituents. This increase appears to be related to the contemporary explosion of interest in healthy foods, supplements and nutraceuticals. It was also probably triggered by large epidemiological studies on fruits and vegetables, and particularly on flavonoids, consumption and incidence of cancer, stroke and coronary heart disease. The widely distributed flavonols constitute the flavonoid subgroup upon which the greatest interest has been focused, followed by flavanols and more recently by anthocyanidins and other related polyphenols such as resveratrol. Research on isoflavones rapidly emerged in the 1990s but plateaued in the 2000s. In the 1990s flavonoids were mainly considered as the active components of medicinal plants, while from 2000 onward, they switched to be mainly regarded as bioactive food ingredients. We envision a continuation in the growth of research for the coming decade focused on clearly demonstrating the importance of flavonoids for human health.

Edward Ballard and the Practice of Epidemiology in the 19th-Century United Kingdom.

This article recovers the history of Victorian epidemiology through the career of British physician Edward Ballard (1820-1897). Ballard's career provides a useful window into the practices of epidemiology in the 19th century because he held notable public health posts as medical officer of health for Islington and inspector at the Medical Department of the Local Government Board. By the time of his death, in 1897, he typified the transition toward professional epidemiology. In exploring some of the most important environmental and health-related problems in preventive medicine in the 19th century, Ballard was part of a group of influential epidemiologists who studied infectious disease. In particular, he was noted for his research into typhoid fever and industrial health. Yet Ballard's career has largely been forgotten. In this article, I explore Ballard's work as a window into the everyday practices of Victorian epidemiology and suggest that the process of professionalizing epidemiology in the 20th century was about forgetting epidemiology's Victorian past as much as it was about championing it.

Eric Wittkower and the foundation of Montréal's Transcultural Psychiatry Research Unit after World War II.

Eric Wittkower founded McGill University's Transcultural Psychiatry Unit in 1955. One year later, he started the first international newsletter in this academic field: Transcultural Psychiatry. However, at the beginning of his career Wittkower gave no signs that he would be interested in social sciences and psychiatry. This paper describes the historical context of the post-war period, when Wittkower founded the research unit in Montréal. I focus on the history of scientific networks and the circulation of knowledge, and particularly on the exchanges between the French- and English-speaking academic cultures in North America and Europe. Because the history of transcultural psychiatry is a transnational history par excellence, this leads necessarily to the question of the reception of this academic field abroad.

An architect for mental health: an appreciation of Michele Tansella.

Michele Tansella, Professor of Psychiatry at the University of Verona, died in 2015. This editorial pays tribute to his contributions to scholarship in the field of psychiatric epidemiology and health service research, and to his highly effective efforts to improve mental healthcare, locally, nationally and internationally.

Epidemiology in Germany-general development and personal experience.

Did you ever hear about epidemiology in Germany? Starting from an epidemiological desert the discipline has grown remarkably, especially during the last 10-15 years: research institutes have been established, research funding has improved, multiple curriculae in Epidemiology and Public Health are offered. This increase has been quite steep, and now the epidemiological infrastructure is much better. Several medium-sized and even big population cohorts are ongoing, and the number and quality of publications from German epidemiologists has reached a respectable level. My own career in epidemiology started in the field of environmental health. After German reunification I concentrated for many years on environmental problems in East Germany and observed the health benefits after improvement of the situation. Later, I concentrated on population-based cohorts in newborns (GINI/LISA) and adults (KORA, German National Cohort), and on biobanking. This Essay describes the development in Germany after worldwar 2, illustrated by examples of research results and build-up of epidemiological infractructures worth mentioning.

Evolution of sanitary-epidemiological services in Poland in the years 1944-2014.

This paper presents the history of sanitary-epidemiological services in the context of the health, economic and socio-political situation in Poland in the years 1944-2014, with a critical analysis of legal restraints, efficiency and achievements. Polish Sanitary Services, established in 1919, as a state service, have preserved for more than 95 years (also during World War II and the occupation) the continuity of its structures and essential objectives to enable their implementation in the field of public health protection. The unique effectiveness of actions was recorded in the years 1954-1998 and 2002-2009 in the time of central (vertical) subordination of sanitary-epidemiological services. The pre-accession preparation to the European Union (EU) strongly accelerated the development of sanitary-epidemiological services in Poland. Polish accession to the European Union has promoted the implementation of the WHO document "Health for All in the 21st Century" and the reduction of "health inequalities".

Epidemiology: Then and Now.

Twenty-five years ago, on the 75th anniversary of the Johns Hopkins Bloomberg School of Public Health, I noted that epidemiologic research was moving away from the traditional approaches used to investigate "epidemics" and their close relationship with preventive medicine. Twenty-five years later, the role of epidemiology as an important contribution to human population research, preventive medicine, and public health is under substantial pressure because of the emphasis on "big data," phenomenology, and personalized medical therapies. Epidemiology is the study of epidemics. The primary role of epidemiology is to identify the epidemics and parameters of interest of host, agent, and environment and to generate and test hypotheses in search of causal pathways. Almost all diseases have a specific distribution in relation to time, place, and person and specific "causes" with high effect sizes. Epidemiology then uses such information to develop interventions and test (through clinical trials and natural experiments) their efficacy and effectiveness. Epidemiology is dependent on new technologies to evaluate improved measurements of host (genomics), epigenetics, identification of agents (metabolomics, proteomics), new technology to evaluate both physical and social environment, and modern methods of data collection. Epidemiology does poorly in studying anything other than epidemics and collections of numerators and denominators without specific hypotheses even with improved statistical methodologies.

Epidemiology and the Tobacco Epidemic: How Research on Tobacco and Health Shaped Epidemiology.

In this article, I provide a perspective on the tobacco epidemic and epidemiology, describing the impact of the tobacco-caused disease epidemic on the field of epidemiology. Although there is an enormous body of epidemiologic evidence on the associations of smoking with health, little systematic attention has been given to how decades of research have affected epidemiology and its practice. I address the many advances that resulted from epidemiologic research on smoking and health, such as demonstration of the utility of observational designs and important parameters (the odds ratio and the population attributable risk), guidelines for causal inference, and systematic review approaches. I also cover unintended and adverse consequences for the field, including the strategy of doubt creation and the recruitment of epidemiologists by the tobacco industry to serve its mission. The paradigm of evidence-based action for addressing noncommunicable diseases began with the need to address the epidemic of tobacco-caused disease, an imperative for action documented by epidemiologic research.

The Johns Hopkins Bloomberg School of Public Health: A Brief History of a Century of Epidemiologic Discovery.

During its first century, the Johns Hopkins University Bloomberg School of Public Health has been home to several faculty members who have played leading roles in defining and expanding the field and science of epidemiology. They have done so by training leaders in the field, creating new methods and applications, and making relevant discoveries in the worlds of infectious and chronic diseases. These methodologic innovations and discoveries underlie many of today's major health policies and practices.

Leadership of the Department of Epidemiology of the Johns Hopkins Bloomberg School of Public Health in Its First Century.

This commentary reviews the contributions of each of the 7 Chairs of the Department of Epidemiology from the Department's inception in 1919 to the advent of the Centennial Celebration of the Johns Hopkins Bloomberg School of Public Health in 2016. The founding Chair, Wade Hampton Frost (1919-1938), was among the handful of foundational thinkers in the discipline of epidemiology. Kenneth Maxcy (1938-1954) and Philip Sartwell (1954-1970) oversaw the Department through the epidemiologic transition from a preponderance of morbidity and mortality due to infectious diseases to a preponderance of noncommunicable diseases. Abraham Lilienfeld (1970-1975) and Leon Gordis (1975-1993) were perhaps best known for their mastery of teaching, influencing generations of both medical and public health students. Jonathan Samet (1994-2008) oversaw a major curriculum revision and expanded the Department significantly, and David Celentano (2008-) is working to rebalance the practice of epidemiology with the etiological foundations of epidemiology. All Chairs were a product of their times, and their research focus and portfolios influenced the direction of the Department. Future generations of Johns Hopkins students will be influenced directly or indirectly by the heritage of these Chairs' actions and those of their faculty.

Ancient Disease, Modern Epidemiology: A Century of Progress in Understanding and Fighting Tuberculosis.

A century's worth of efforts to better understand the epidemiology of tuberculosis (TB) and to develop new vaccines, drugs, preventive interventions, and case-finding approaches have provided important insights and helped to advance the field of epidemiology as a whole. Wade Hampton Frost developed methods for cohort analysis that formed the early basis for adjustment of confounding variables. The streptomycin trial in the United Kingdom in the 1940s introduced random allocation for participants to either the treatment or control group, ensuring blinded treatment assignment and comparable treatment groups, which is now a key element in randomized clinical trials. Research into the bacille Calmette-Guérin vaccine demonstrated the importance of comparative analyses, potential difficulties in generalizability to populations not under study, and the role of meta-analysis for discrepant data-approaches now strongly recommended prior to implementing any novel public health intervention. George Comstock's work on preventive therapy for TB demonstrated the use of epidemiologic methods to evaluate interventions on a population level. Finally, studies from the Consortium to Respond Effectively to the AIDS/TB Epidemic focused on the evaluation of real-world effectiveness and of targeting of high-risk subpopulations. In this article, we discuss how TB research in each of these domains has helped to advance epidemiologic thinking and methodology over the past 100 years.

Mechanistic Models of Infectious Disease and Their Impact on Public Health.

From the 1930s through the 1940s, Lowell Reed and Wade Hampton Frost used mathematical models and mechanical epidemic simulators as research tools and to teach epidemic theory to students at the Johns Hopkins Bloomberg School of Public Health (then the School of Hygiene and Public Health). Since that time, modeling has become an integral part of epidemiology and public health. Models have been used for explanatory and inferential purposes, as well as in planning and implementing public health responses. In this article, we review a selection of developments in the history of modeling of infectious disease dynamics over the past 100 years. We also identify trends in model development and use and speculate as to the future use of models in infectious disease dynamics.

The Role of Professional Journals and Societies in the Future of a Field: A Reflection on the Partnership Between the American Journal of Epidemiology and the Society for Epidemiologic Research.

On this, the 100th anniversary of Johns Hopkins Bloomberg School of Public Health, we take the opportunity to reflect on the ties between the School, the American Journal of Epidemiology, and the Society for Epidemiologic Research. We discuss briefly the intersection of the School, the Journal, and the Society throughout their histories, with the aim of providing some insight into how the Journal and the Society have contributed to the evolution of the field. In so doing, we articulate the challenges that the Journal and the Society jointly face today, with an eye to finding opportunities in these challenges that can be helpful in coming decades.