Overview: Medicine 1950-present

During the twentieth century, medical theory and practice underwent more profound changes than in all of the years since the time of Hippocrates (460?-377? b.c.). Since World War II, changes in science and society have transformed the theoretical, institutional, educational, economic, and ethical foundations of medicine. For example, research on the growth of stem cells has sparked both hope for revolutionary medical applications and profound ethical challenges. In 1999 the editors of the journal Science selected stem cell research as the "Breakthrough of the Year." Embryonic stem cells could be used to produce specific types of cells and tissues. Eventually, stem cells might be used to build new body parts to replace failing human organs.

Nineteenth-century scientists and physicians introduced the modern germ theory of disease and made it possible to identify the cause and means of transmission of many infectious diseases. Since 1950 many of the most feared infectious epidemic diseases have been brought under control by means of preventive vaccines, antibiotics, public health measures, and improvements in sanitation. Preventive immunizations for infectious epidemic diseases began with inoculation and vaccination against smallpox. The global eradication of smallpox in the 1970s is one of the greatest achievements of twentieth-century public health medicine and a model for international cooperation. Public health authorities hoped that the lessons learned in the smallpox campaign would lead to global immunization programs for controlling or eradicating poliomyelitis, measles, whooping cough, diphtheria, and tuberculosis. The Salk and Sabin vaccines for poliomyelitis essentially ended the threat of this disease in the wealthy, industrialized nations. Nevertheless, debates about the safety and efficacy of preventive vaccines continue.

Advances in the science of virology, bacteriology, immunology, and molecular biology have led to new approaches to the construction of vaccines. At least 15 new or improved vaccines were developed between 1980 and 2000. Experimental vaccines developed in the 1990s may offer enhanced protection against influenza, pneumococcal pneumonia, pertussis, rubella, rabies, bacterial meningitis, hepatitis B, and adenovirus-associated respiratory disease. New vaccine technologies also offer hope of ameliorating the effects of autoimmune disorders and allergies. Of course, in much of the world old specters, such as tuberculosis, malaria, measles, poverty, and malnutrition, remain major threats to life. Historians have called malaria the most devastating disease in history. Malaria and other "tropical diseases" are still major public health threat in many parts of the world.

In the twentieth century, the chronic diseases, especially those that seem to be related to diet and obesity, have eclipsed the threat of infectious disease. By the second half of the twentieth century, heart disease, cancer, and stroke had replaced the infectious, epidemic diseases as the leading causes of death in the United States. Epidemiologists and health policy experts in the 1960s predicted that, at least in the wealthy, industrialized nations, chronic, degenerative diseases would replace infectious diseases as the only significant public health problems. Newly emerging diseases, such as Ebola fever and newly discovered forms of pathogens, such as prions, have challenged that concept. Prions have been identified as the cause of a virulent new form of Creutzfeldt-Jakob Disease that is related to "Mad Cow Disease."

Moreover, the global epidemic of AIDS continues to escalate. AIDS first appeared as a diagnostic entity in 1981 when the Centers for Disease Control (CDC) began to report strange clusters of rare illnesses associated with a severely compromised condition of the immune system in previously healthy homosexual men in New York and California. By 1984, when the human immunodeficiency virus (HIV), the retrovirus that causes AIDS, was discovered, more than one million Americans were infected with HIV. The World Health Organization reported that five to 10 million people were infected with HIV by the 1990s. Advances in anti-viral therapy have extended the life expectancy of patients with HIV/AIDS, but such drugs cause adverse side effects and are extremely expensive.

In the first half of the twentieth century Paul Ehrlich's (1854-1915) discovery of Salvarsan for the treatment of syphilis and Gerhard Domagk's (1895-1964) discovery of sulfanilamide stimulated the search for more "magic bullets" to fight bacterial infections. By the end of World War II, the problem of drug-resistant strains of bacteria was already compromising the effectiveness of the "sulfa" drugs. The same problem would plague all the antibiotics that were discovered in the second half of the century. Although Alexander Fleming (1881-1955) discovered penicillin in 1928, it remained a laboratory curiosity until research and development during World War II led to the isolation and large-scale production of the drug that has been called the greatest therapeutic advance of all time.

Immunology is a relatively young field, but its twentieth-century evolution has been so dynamic that it has become one of the fundamental disciplines of modern medicine and biology. Throughout the 1970s and 1980s immunologists were awarded Nobel Prizes for achievements of remarkable theoretical and practical significance in understanding organ transplant rejection and autoimmune diseases. One of the most important methodological breakthroughs in medical science in the 1970s was the production of monoclonal antibodies. As cardiovascular disease and cancer replaced infectious diseases as the leading causes of morbidity and mortality in the wealthy, industrialized nations, immunology seemed to offer the answer to the riddle of health and disease just as microbiology had provided answers to the diseases that had posed the greatest threats in the nineteenth century. Research linking immunology and molecular biology has created a new generation of weapons in the battle against cancer, autoimmune disorders, organ rejection, and infectious diseases.

Immunobiology and neuroendocrinology are providing insights into AIDS, cancer, rheumatoid arthritis, and mind-body medicine. After centuries of confusion about the basic causes of cancer, scientists are gaining insights into the factors that cause the loss of control of cell multiplication that is the fundamental characteristic of cancer cells. A cure for cancer remains elusive, but many promising experimental approaches to diagnosis and treatment, based on developments in immunology and molecular biology, were undergoing clinical trials by the end of the 1990s.

Among the most remarkable changes in medical practice over the course of the last 200 years involves the use of technological aids for the diagnosis of disease. With the development of sophisticated new instruments and ways of looking at the human body, specialization became a fundamental aspect of the medical profession. Beyond their obvious role in transforming the art of diagnosis, medical instruments have profoundly affected the relationship between patient and physician, the education and practical training of physicians, the demarcation between areas of medical specialization, the locus of medical practice, and even the financial base of medical care and treatment.

With medical costs skyrocketing, critics of our very unsystematic "health care system" have called for increased attention to preventive medicine and health education. Progress in surgery made possible by advances in technology, such as the heart-lung machine, diagnostic screening devices such as magnetic resonance imaging (MRI), critical care units, and intensive care units are among the factors that increase the costs of modern medicine. Organ transplant operations and the development of artificial organs have saved lives, but are among the most expensive interventions of modern medicine.

Over half of the deaths in the United States are caused by cardiovascular diseases. Many of these deaths could be prevented by aggressive management and surgical procedures, including heart transplant operations. The shortage of donor hearts led to hope that a totally implantable mechanical device could overcome the shortage of donor hearts and avoid the problem of immunological rejection. Early attempts to implant a permanent artificial heart were criticized as premature human experiments. In addition to human heart transplants, heart assist devices, and artificial hearts, animal tissues and organs, or combinations of living cells and artificial materials might eventually be used to assist or replace ailing hearts. Scientists are attempting to grow heart muscle tissue, heart valves, and blood vessels in the laboratory, or modify animal organs so human recipients will not reject them. Other scientists believe that much of the social and individual burden of heart disease could be prevented through changes in diet, exercise, and the elimination of smoking.

Because of changing patterns of mortality and morbidity, the wealthy industrialized nations are increasingly faced with concerns about the medical needs of aging populations. In 1975 the National Conference on Preventive Medicine warned that therapeutic medicine might have reached a point of diminishing returns. Doctors are increasingly called upon to treat the preventable diseases of affluence, such as obesity and arteriosclerosis, with every technological weapon at their disposal. When misused or misapplied, however, the results can be as deadly as the diseases they were designed to treat. Indeed, a study of medical errors released in November 1999 by the National Academy of Sciences and the Institute of Medicine (entitled "To Err is Human") revealed that between 44,000 and 98,000 Americans die each year as a result of medical mistakes. Even the lower range of the estimate is greater than the toll taken by automobile accidents, cancer, or AIDS.

Understanding the complex relationships that link health, disease, demography, geography, ecology, and economics, and the differences in patterns of disease found in wealthy nations and developing nations, remains a major challenge. New approaches to understanding, diagnosis, preventing, and treating disease, and the emergence of new diseases in the late twentieth century demonstrate the need for a global and historic perspective in medicine and the biomedical sciences.

LOIS N. MAGNER