The Public Health Revolution
Pandemics led to the public health revolution in developed countries in the aftermath of the Industrial Revolution, massive migration from rural areas to cities, and the emergence of overcrowded and filthy slums inhabited by the working classes. A comprehensive definition of ‘public health’ is:
Public health is the science and art of preventing disease, prolonging life, and promoting physical health and efficiency through organized community efforts for the sanitation of the environment, the control of community infections, the education of the individual in the principles of personal hygiene, the organization of medical and nursing services for the early diagnosis and preventive treatment of disease, and the development of social machinery which will ensure to every individual in the community a standard of living adequate for the maintenance of health.
The goal of public health is to create a conducive environment to promote the health of the community and prevent diseases. It adopts two broad approaches: population-based and clinical. The population-based approach delves into the social and environmental determinants of health: congested housing, poor sanitation, lack of sewers, polluted air, etc. Clinical methods focus on screening, counseling, and treatment of diseases in clinical settings. As many socio-environmental and biological factors influence health outcomes, the practice of public health does not rely on any specific body of knowledge. It rather applies a mix of science and social management approaches, depending on the context.
The growth of scientific knowledge about diseases, the development of means to prevent and control them, social reforms promoting the value of hygiene and health, and the organization of public institutions, including the empowerment of municipalities to implement interventions, were the pillars of the public health movement in developed countries. These countries made enormous investments in public health, related infrastructure, and spatial planning to maximize the benefits of urban development while minimizing its negative consequences, such as congestion, disease, etc. For example, the cholera eruption in nineteenth-century London led to huge national investments in water supply, sewerage, drainage, and sanitation in the city. The tuberculosis outbreak in the twentieth century in New York City resulted in improvements in tenement regulations, housing reforms, and public transit. The SARS pandemic in the twenty-first century in Asia led to significant upgrading of medical infrastructure and scientific mapping of the spread of disease to enable focused interventions by public health authorities.
Advances in public health have significantly impacted nations through a reduction in mortality, an increase in longevity, and a rise in labor productivity. Life expectancy at birth in industrialized countries rose from 45 years to 75 years during the twentieth century. The majority of the gain – 25 out of 30 years – is attributed to public health improvements, including better nutrition, sanitation, safer housing, and other non-medical factors. The largest gains in life expectancy in the United States occurred between 1880 and 1920 due to infectious disease control, clean water, and sanitation. to three phases of ‘mortality transition.’ In the first phase – from the middle of the eighteenth to the middle of the nineteenth century, improvements in nutrition, economic growth, and incipient public health measures might have played a key role. In the second phase – from the last decades of the nineteenth century to the first decades of the twentieth, public health developments overwhelmingly dominated the factors contributing to mortality reduction. These include improvements in water supply and sanitation, food safety, vaccination, and efforts to improve personal hygiene. The third phase – from the 1930s – is the era of big medicine, marked by antibiotics, new vaccines following advances in bacteriology, and intensive personal interventions that characterize the modern medical system.