Public health services can prevent premature death from epidemics such as the plague, cholera, and many other infectious and environmentally determined diseases; and enhance the quality of life. Public health is among the most important institutions of organized societies, almost entirely responsible for the immense improvements in life expectancy everywhere in the world in the past 150 years. Its aims are to promote, protect, and preserve good health, and to sustain people when disabilities render them incapable of fending for themselves. Public health is practiced by a team of specialists trained in medicine, nursing, sanitary engineering, environmental, social, and behavioral sciences, health education, administration, and a variety of other fields. In many nations, including the United States, public health is organized hierarchically at national, regional, and local levels.
Public health services are distinguished from other aspects of the health care system because they are financed by taxation, with no fees paid by the users of these services. This phenomenon can lead to funding crises and staff layoffs when there is political pressure to cut taxes. People and their political representatives often take their health for granted when no epidemics threaten them, so they are not motivated to maintain public health services, staff, and infrastructure at a high level of efficiency and effectiveness, even though ensuring public health is an essential component of the health care system. No nation remains healthy if public health services break down, as they did in Russia after the collapse of the Soviet Union. In this case, infant mortality rates rose, life expectancy fell, and epidemics of diphtheria, typhoid, and other lethal infections occurred. Public health services are as vital to national security as efficient armed forces and the police and fire services. The people of the United States recognized this fact when cases of anthrax occurred in 2001, caused by the introduction of anthrax spores into letters sent through the U.S. Postal Service.
Since the origins of agriculture and permanent settlements 10,000 years ago, human progress has been punctuated by deadly epidemics. Often arising seemingly out of nowhere, they cut a swath through the population, arousing fear among victims and survivors alike. They were perceived as due to the wrath of a vengeful god, retribution for sinful conduct, or manifestations of evil spirits. Before their causes were understood, survivors full of grief and rage sometimes blamed witches, or those perennial scapegoats, the Jews, extracting vengeance by burning them at the stake or conducting pogroms. Epidemics of plague, smallpox, typhus, cholera, malaria, influenza, and measles have contributed to the fall of civilizations and the defeats of campaigning armies, and they have long fascinated historians as well as epidemiologists. Biblical stories of epidemics indicate the people of those times encountered smallpox and bubonic plague. The historian Thucydides described the plague that decimated the Athenian forces at the end of the first year of the Peloponnesian War (426 B.C.E. ), but despite his meticulous description (based partly on having had it himself) the cause remains uncertain. It may have been influenza complicated by bacterial infection. The vitality of the late Roman Empire (200–400 C.E. ) was sapped by two diseases better described as endemic than epidemic—malaria, spread by mosquitoes in the Pontine marshes nearby, and lead poisoning, caused by drinking from cups made of tin-lead alloys.
The greatest of all epidemics was the Black Death, which entered Europe at Genoa on ships trading from Asia Minor in 1347, and spread over the next two to three years until it had laid waste to the entire continent. The Black Death killed at least one-third of the population. Sometimes whole villages were wiped out and, in cities such as Paris, organized life and everyday commerce came to a halt. Plague had struck before, for instance at the time of Justinian (543 C.E. ), and continued to cause occasional epidemics such as the one in London in 1665 described in Samuel Pepys's diary. However, society had not seen anything on the scale of the pandemic of 1347–1349. The plague bacillus primarily infects rodents and is transmitted by the rats' fleas. Human epidemics occur when ecological conditions bring rats, their fleas, and people together at close quarters in dirty, verminous conditions.
Typhus, caused by a microorganism called Rickettsia, a small bacterium, is spread by the body louse. Epidemics of typhus occur when large numbers of people are confined in close quarters in dirty, verminous clothing (e.g., war refugees and campaigning armies). An impending epidemic that would have had a serious strategic impact was stopped in Naples in 1944 by liberal use of the insecticide DDT. In his classic work Rats, Lice and History (1935), the microbiologist Hans Zinsser vividly describes how the outcome of wars has often been decided by which side was more successful in withstanding the deaths from typhus among its fighting forces. The European conquest of the Americas and colonization of the rest of the world was materially assisted by the impact of measles, smallpox, and tuberculosis on the people who had been there before them. Europeans had some inherent resistance to those diseases after many centuries of exposure had weeded out those most susceptible. The Allied campaigns in the Pacific during World War II were facilitated by the fact that American, Australian, Indian, and British forces had effective anti-malarial agents and their Japanese adversaries did not. This fact may have played a larger part in the victory than the atom bombs dropped on Hiroshima and Nagasaki.
In the eighteenth and nineteenth centuries an arrogant assumption by medical men that they could lay their healing hands upon women in childbirth—even when those hands were laden with dangerous bacteria—led to a tragic epidemic of fatal childbed fever. The epidemic ended only when the studies of Ignaz Semmelweiss in Vienna and Budapest and Oliver Wendell Holmes in Boston in the 1840s were translated into hand washing in antiseptic lotion. The use of antisepsis in labor wards and operating rooms, as practiced and advocated by the surgeon Joseph Lister, followed hand washing more than twenty years later.
In the late twentieth and early twenty-first centuries, the HIV/AIDS (human immunodeficiency virus/acquired immunodeficiency syndrome) pandemic had a catastrophic impact on sub-Saharan Africa, comparable to the Black Death in medieval Europe except for the different course of the disease. The plague killed in a few days and HIV/ AIDS takes a few years, but the ultimate death rate is higher, approaching 100 percent, whereas at its worst the Black Death killed between 70 percent and 80 percent of its victims. By the end of the twentieth century, HIV/AIDS afflicted more than 40 million people and killed 30 million people.
With the insights of modern evolutionary biology and medical sciences, researchers know that epidemics and many other widely prevalent diseases originated from and are perpetuated by a combination of ecological conditions. Malaria, yellow fever, other vector-borne diseases, and many parasitic infections probably first occurred in humans as a result of evolutionary developments in the causative agents and their vectors. Smallpox, influenza, measles, plague, and several other epidemic diseases probably first afflicted humans by "jumping species" from their origins as diseases of animals that were domesticated by Palaeolithic humans.
In the second half of the twentieth century, most people in the rich industrial nations were able to live long and healthy lives, but as many as 30 to 40 percent of middle-aged men were dying before their potential life span of lung cancer or coronary heart disease, two modern epidemic diseases often attributable to tobacco addiction. Undeterred by the massive evidence that their product is the most powerful addictive substance known, and lethal if used as the manufacturers intended, the tobacco manufacturers embarked upon aggressive and successful campaigns to market cigarettes to girls and women who had previously not often smoked. The result is that lung cancer death rates among women began to rise sharply in the final two decades of the twentieth century, and can be confidently predicted to keep rising so long as women continue to fall victim to tobacco addiction. Similar aggressive and unprincipled tobacco marketing campaigns are being conducted throughout the developing nations in the early twenty-first century. The World Health Organization estimates that the annual number of deaths from tobacco-related diseases could reach 8 to 10 million worldwide by 2025 as a result. This would make tobacco addiction a lethal epidemic disease comparable to if not greater in magnitude than HIV/AIDS.
Historical Origins of Public Health
Contemporary public health services began in the middle of the nineteenth century in response to the squalid conditions that existed in the rapidly growing cities and towns of the industrial revolution. These cities and towns were dangerous places. In the early nineteenth century, a newborn had about one chance in four or five of dying before his or her first birthday, and only about half survived long enough to grow up and have children of their own. They died of diarrheal diseases, including cholera, or of respiratory infections, such as bronchitis, measles, croup, pneumonia, and tuberculosis. Life expectancy in the new industrial towns was only about thirty-five years. This appalling situation challenged the emerging medical sciences and the social reformers to act. Aided by an expanding knowledge and understanding of the times, their efforts led to reduction of infant mortality rates and rising life expectancy. By 1900 infant mortality rates in the industrial nations had fallen to about 100 per 1,000 live births, and life expectancy had risen to about 45 to 50 years. By 1950 infant mortality rates were down to about 40 per 1,000 live births and life expectancy was at or above seventy to eighty years in most of the industrial nations. By 1999 infant mortality rates were below 10 per 1,000, and life expectancy approached 80 years, even in the United States, which has traditionally lagged behind many other wealthy industrial nations.
Social, medical, and public health reform originated largely in England, but took place almost simultaneously throughout much of Western Europe and the United States. A combination of several essential factors made possible these reforms, collectively known as the sanitary revolution. The same essential factors must exist before almost any public health problem can be resolved. These include an awareness that the problem exists; an understanding of what is causing it; the capability to control the cause or causes; belief that the problem is important enough to tackle; and political will.
An awareness that the problem exists. In the middle to late nineteenth century, awareness was facilitated by rising literacy, the availability of newspapers, and the development of vital statistics that provided documentary evidence of the magnitude of the problem of deaths from diarrheal diseases and respiratory infections in infancy, childhood, and early adult life. Since the mid–twentieth century, television has played an increasingly important role in drawing attention to new public health problems, such as those associated with toxic pollution of the environment.
An understanding of what is causing it. John Snow, the English physician who investigated the cholera epidemics in London in the 1840s and 1850s, provided evidence that the disease was spread by polluted drinking water. The cholera vibrio, the causative organism, was not discovered until about thirty years later, but recognition that polluted water was spreading cholera enabled some preventive action—provision of clean water supplies—to begin.
Capability to control the cause or causes. Oliver Wendell Holmes and Ignaz Semmelweis demonstrated that washing hands in a disinfectant could prevent most cases of childbed fever. Both men were vilified by their colleagues who regarded it as an insulting slur on their character to imply that their dirty hands caused the disease. Joseph Lister was successful because his carbolic spray implied that the cause was not necessarily the unhygienic habits of the doctors but rather bacteria in the air in operating rooms and lying-in wards in hospitals. By then, many varieties of dangerous bacteria had been discovered and linked to the diseases that they caused.
Belief that the problem is important enough to tackle. Historically, a mounting emotion of public outrage about what is perceived to be an intolerable burden upon the people is the catalyst for change. The phrase "filth diseases" evokes the distaste for unhygienic conditions that contributed to the burden of premature deaths in nineteenth-century industrial Britain. Geoffrey Vickers, a British social policy specialist, referred to this rising public outrage as "redefining the unacceptable"—a phrase that captures the essential factor in setting a new goal for public health.
Political will. A public health problem will persist unless there is determination to correct the conditions that cause it. This usually means disturbing the status quo and encroaching upon the livelihood of individuals and often powerful interest groups—slum landlords, nineteenth-century water supply companies, twentieth-century tobacco manufacturers, and twenty-first-century industry, energy, and transport sectors resisting action to control global climate change. Moreover, it costs money to make the necessary changes, which usually results in additional taxes and extended political debate.
Methods of Public Health
Health can be preserved, protected, and promoted in several ways, including ensuring the environment is safe, enhancing immunity, and living a healthy lifestyle.
Ensuring the environment is safe. A safe environment includes drinking water that is free from dangerous pathogenic organisms and toxic substances. This requires purification of public water supplies, a sanitation service with efficient sewage disposal, and safeguards against contamination of water and food supplies by pathogens and toxic chemicals. In modern urban industrial societies clean air is another part of the natural environment that must be protected: clean indoor air, free from tobacco smoke, as well as urban air free from smog. Efforts to clean both outdoor and indoor air are often initially resisted by various interest groups.
Enhancing immunity. Immunity is enhanced by vaccination or immunization against infectious diseases in infancy and childhood. Vaccination against smallpox began after Edward Jenner, a physician in Gloucestershire, England, experimented on his patients with cowpox lymph in the late eighteenth century. His results, published in An Inquiry into the Variolae Vaccinae (1798) were perhaps the single most important public health advance of the second millennium. Smallpox had long been one of the great epidemic scourges. It killed 40 percent or more of all who were infected by the virus, and disfigured, sometimes blinded, many more. Within one hundred years it had been brought under control in most parts of the world and in 1980, after a determined global eradication campaign, the World Health Organization proclaimed the worldwide eradication of smallpox. Vaccines and sera containing immunizing agents have been developed against many other dangerous and often lethal infectious agents. See Table 1 for a list of the most important, all of which (except polio) caused innumerable premature deaths. Vaccines to prevent smallpox and rabies, two deadly virus diseases, were developed long before the agent was discovered, which had to await the invention of the electron microscope. Discovery of the bacterial agents responsible for many other dangerous infections occurred rapidly in the late nineteenth century, following the development of high-quality microscopes and the techniques of bacterial culture.
Living a healthy lifestyle. Living a healthy lifestyle means abiding by the maxim of the ancient Greeks, "Nothing to excess." It includes avoiding harmful addictive substances, especially tobacco, and adhering to a balanced diet and regular exercise program. Living a healthy lifestyle can be encouraged by health education campaigns. Adhering to a balanced diet—comprised of the right mix of protein, fats, and carbohydrates, with vitamins and essential trace elements—is necessary to achieve good health and prevent premature death. Famine conditions have killed populations of people in the past, partly from starvation itself but also because malnutrition makes people, especially children, vulnerable to deadly infections such as measles, and reduces resistance to tuberculosis.
Other methods of public health include carefully nurturing the next generation; ensuring that children are well-borne and do not have inherent genetic defects or malformations that result from exposure to toxic substances; and prudent use of diagnostic and therapeutic medical services (i.e., avoiding multiple and often needless exposures to diagnostic X rays, coronary artery surgery for elderly people at the upper extremity of the life span, and cosmetic breast implants), which can be harmful if improperly applied.
Last, John M. Public Health and Human Ecology, 2nd edition. New York: McGraw-Hill, 1997.
McMichael, A. J. Human Frontiers, Environment, and Disease: Past Patterns, Uncertain Futures. Cambridge: Cambridge University Press, 2001.
McNeill, William Hardy. Plagues and Peoples. Garden City, NY: Anchor Press, 1976.
Snow, J. Snow on Cholera, edited and annotated by W. H. Frost. 1936. Reprint, New York: Hafner Publishing, 1965.
Zinsser, Hans. Rats, Lice and History. Boston: Little, Brown, 1935.
JOHN M. LAST