Public health, which is dedicated to promoting wellness and preventing disease and injury at the community level,1 has played an important role in improving quality of life since the beginning of human civilization. During the mid-19th century, the field experienced significant advancements as scientists and healthcare professionals pioneered new ways to analyze population-level information. Figures such as Florence Nightingale and Dr. John Snow are particularly notable for their early use of quantitative data to ascertain the root cause of public health crises, and many of the principles derived from their efforts have been successfully applied to modern-day public health emergencies.

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     In the heat of the Crimean War, Florence Nightingale, a British nurse, statistician, and social reformer who was given the title “Lady with the Lamp” for spending nights providing personal care to soldiers, observed mounting British casualties in the camps due to illnesses like cholera.2 Calling the diagrams “coxcombs” (which are similar to modern pie charts, but instead of segments which are proportionate to the whole and represent parts of a percentage, they feature equal-angle sectors with varying radii), she pioneered the polar area diagrams in medicine to visualize the sources of patient mortality2 (Note: while Nightingale made the pie chart more readable, she did not actually invent it, contrary to popular belief; it was actually the Scottish engineer and political economist William Playfair who introduced the graphic in 1801, just another example of how ideas can cross disciplines and promote progress).3 Through her analysis, Nightingale discovered that poor sanitation and overcrowding of military encampments and hospitals, which led to the widespread proliferation of diseases like cholera, was one of the key causes in high mortality rates among British soldiers stationed at home, especially when compared to the battlefield.2 The nurse would continue to study and collect data on sanitation, presenting findings from the war to illustrate the magnitude of unsanitary conditions and from rural India to advocate for improved medical care and public health service in India. Exasperated with inaccurate and missing data contained in official reports, she also sought to improve the data collection methods utilized by the British army.4 Nightingale’s emphasis on data-driven decision-making, utilization of new data visualization techniques to improve readability, and improving data stewardship have had a tremendous influence on how experts track and statistically analyze public health crises in the modern day.5

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     Another key step in the advancement of public health is John Snow and his early use of epidemiology, the study of “the distribution and determinants of diseases or disorders within groups of people,”6 to solve a key public health issue, namely the cholera epidemic originating from the Broad Street pump in London. Growing up in an unsanitary environment in York, England and treating patients amidst a disease outbreak in his adolescence provided Snow with important experience in fighting diseases. As he moved to London to study medicine and practice as an anesthesiologist, Snow undertook an independent investigation of a cholera epidemic afflicting his district.7

 

     Snow had been a skeptic of the then-dominant miasma theory, which posited that disease was caused by “bad air” (germ theory was still held among a minority of scientists at this time), and concluded that the root cause of the disease was through ingestion rather than inhalation.7 Enlisting the help of Rev. Henry Whitehead, a trusted figure in the local community who was concerned for the well-being of his parishioners and also sought to understand why an awful disease had fallen upon them,8 Snow successfully reached out to local residents and interviewed them about their concerns. This information helped Snow identify the source of the outbreak to a water pump on Broad Street.7 To corroborate his findings on the geographic origin, he began constructing a dot map, with each dot representing a water pump, and generated regions representing all the points on the map which were closest to each pump (also known as a Voronoi diagram). (Note: In a Voronoi diagram, a space is divided into regions based on the distance to a set of given points. Each region contains the space closest to a certain point).9 From this spatial visualization and a following statistical comparison between the Broad Street pump and the Seething Wells pump, which drew cleaner water from further upstream,10 Snow was able to triangulate the source and confirm his conclusions. He relayed his findings to the local government, which eventually removed the pump’s handle but rejected Snow’s theory on the fecal-oral route of disease transmission. After several other outbreaks involving contaminated water, Snow’s work and findings eventually began to gain more widespread acceptance, and engineers like Sir Joseph Bazalgette worked with Members of Parliament to construct large enclosed sewers, revolutionary technology of the time, along the Thames River, greatly mitigating the spread.8 Snow’s work is considered a groundbreaking step in epidemiology and public health, as he had recognized that treating disease necessitates viewing the larger environment and not just individual isolated cases. Similar to Nightingale, Snow meticulously collected data, mapping out the cases to track the spread of disease and using geographic correlations to make conclusions, tools and techniques that are vital to the work of epidemiologists to this day. Additionally, Snow recognized the importance of acting quickly and shutting down the water pump before more patients became ill and needed treatment.

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     Out of the myriad lessons that public health experts have taken away from these pivotal cases and many others, I will focus on three in particular which have had the greatest impact on the current day and on a modern public health challenge: the COVID-19 pandemic.

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     When John Snow was investigating the spread of cholera among Soho, London, he noted the squalid conditions in which many of the community’s residents lived, highlighting the profound impact of the social determinants of health (including environmental conditions, economic stability, and education level).11 Snow’s work helped public health officials realize the importance of improving sanitation and access to clean water to mitigate outbreaks,7 especially in underserved communities where they were more likely to originate. These lessons carried over to subsequent health crises such as the 1947 smallpox outbreak in New York City, where city health officials led by Dr. Israel Weinstein opened free clinics12 to ensure widespread vaccine accessibility and gave daily radio addresses to alert the public about the dangers of smallpox and assuage fears surrounding inoculation.13 The response has been lauded for its rapid response and mass vaccination effort, an example of decisive action taken to handle a public health crisis. Through their community-based interventions, both Snow and Weinstein demonstrated the bioethical principle of justice, which can be defined as the fair and equitable distribution of healthcare resources,14 by identifying the impact that disease outbreaks have on vulnerable communities.

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     These lessons have been particularly relevant during the COVID-19 pandemic, as marginalized communities bore a disproportionate burden of the virus. Across the United States, public health officials utilized targeted interventions to address disparities in health; for example, to reduce the impact of having to travel great distances to receive care, officials in Greenbrier County, West Virginia opened mobile testing units for rural residents to receive rapid COVID-19 tests without leaving their homes.15 Officials also partnered with the West Virginia School of Medicine (WVSOM) and a bus transport network to provide free transportation for residents of the community attending non-emergency medical appointments.15 Additionally, experts sought to address the root causes of skepticism towards vaccines. The Public Health Alliance of Southern California began a video series to highlight efforts and initiatives across the country which seek to provide easier access to getting vaccinated for individuals with disabilities, use data-driven strategies to reach communities of color, and work with faith-based organizations to dispel widely-held misconceptions about vaccinations and increase the vaccination rate.16

 

     The use of data as a foundation for public health interventions is another key lesson from Snow and Nightingale. Snow employed data to scientifically validate the source of cholera, mapping cases to uncover patterns and identify solutions, while Nightingale used statistical analysis to promote better sanitary conditions in hospital wards and reduce mortality rates. This respect for evidence-based decision-making continues to shape public responses. During the pandemic, scientists worked tirelessly to develop a treatment for the SARS-CoV-2 virus using novel technologies like mRNA and adenovirus vector vaccines17,18 and leveraging decades of research in molecular biology and statistical modeling to predict and test efficacy, exemplifying the power of scientific innovation. Public health experts at the CDC also utilized data to identify the recipients of programs such as the free mobile testing units in West Virginia, collecting “racial, ethnic, and socioeconomic data for COVID-19 testing, cases, hospitalizations, and deaths”19 in addition to data from supplemental sources such as emergency department data on COVID-19 and “ad hoc surveys on attitudes and beliefs.”19 This approach to addressing health disparities and striving to improve health justice by combining quantitative and qualitative data shares similarities with both Nightingale and Snow’s approaches, as they combined their close observation of living conditions and hygiene practices with meticulously collected data. Their reliance on data transformed public health in their time and continues to inspire contemporary breakthroughs which have saved countless lives.

 

     Snow and Nightingale’s experiences have reaffirmed the importance of interdisciplinary collaboration between public health experts, scientists, policymakers, and other members of the community. Notably, John Snow’s research on the spread of cholera from the infected pump inspired Sir Joseph Bazalgette’s redesign of London’s sewer system and greatly improved the city’s cleanliness,8 signifying how interdisciplinary partnerships can lead to systemic change. In addition, despite holding disparate beliefs on disease transmission, Snow and Rev. Whitehead teamed up to investigate the cholera outbreak, and Snow was able to have invaluable discussions with various members of the community who were reassured by Whitehead’s presence and authority.8 During the COVID-19 pandemic, agencies like the CDC, NIH, and Department of Health and Human Services (HHS) have worked with community leaders and federal lawmakers across America to address the impact of the pandemic, supporting legislation like the American Rescue Plan, which passed in March 2021. The ARP, among its many objectives, allocated funding towards mental and behavioral training in addition to more widespread testing and detection of COVID-19,20 expanded the premium tax credit (PTC) to improve healthcare access,21 and provided resources to prepare the country for future pandemics and public health crises.20 Conducting a study to ascertain the impact of the American Rescue Plan, healthcare economists Aina Katsikas and Sankar Mukhopadhyay at the University of Nevada noted that the law boosted overall insurance coverage, reduced racial disparities, and contributed to advancing health equity.21

 

     Florence Nightingale and John Snow are widely recognized trailblazers in public health, having pioneered a data-driven approach to addressing health crises. Their work continues to inspire modern experts who use innovative, data-based techniques to tackle health disparities and collaborate across disciplines. The enduring principles demonstrated by them are critical as society navigates current challenges and prepares for future ones, underscoring the lasting impact of their contributions to public health.