The second half of the century saw an increasing number of discoveries, and the practice of science and medicine grew ever closer. In developed countries, the expansion of private insurance programs and government-sponsored coverage have delivered effective health care to most citizens of those countries. Children in the United States now typically receive twenty immunizations against eleven diseases before they are two years old. Whereas at the start of the twentieth century, no more than half of all children reached adulthood, basic sanitation and vaccination campaigns make it possible for most children in industrialized nations to grow up.

Chronic diseases of affluence (obesity, cancer, heart disease, and geriatric conditions), as opposed to infectious diseases, now preoccupy health care providers in developed countries. Plastic surgery enables the affluent to pursue culturally conditioned images of beauty. The birth control pill, other forms of birth control, the availability of abortions, and antibiotics for the more common sexually transmitted diseases have enabled a change in sexual mores throughout the developed world.

In developing countries, improvements in basic sanitation and basic vaccination against childhood diseases have dramatically dropped mortality rates and helped these countries surge in population. Infectious diseases have continued to be a major problem. Many developing countries lie along the equator, and malaria, the greatest remaining scourge, still kills millions annually and incapacitates many millions more. Development of an effective vaccination against malaria has struggled in the face of neglect by the citizens of developed countries, who are rarely personally affected by the disease, and the intrinsic difficulty of the problem. Mosquito control by synthetic pesticides such as DDT (dichloro-diphenyl-trichloro-ethane) proved effective, but too expensive, and the side effects of the pesticides are now better appreciated.

The Austrian-born Canadian endocrinologist Hans Selye (1907–1982) demonstrated how physiological stress affects the human body, fundamentally changing the perspectives of scientists on how hormones and other chemicals in the body react to stress. Physicians came to accept that physiological stress could contribute to many problems, including heart attacks, arthritis, allergies, kidney disease, and inflammatory tissue diseases.

A United Nations doctor examines a child in Mzimzina, Uganda, in 1967.

(Corel Corporation)

Improvements in technology provided new tools for diagnosis and treatment. The heart-lung machine, invented by the physician John H. Gibbon (1903–1956), was first successfully used in 1953, enabling the heart and lungs to be stopped, their functions performed by the machine, while doctors operated. The development of computerized tomography (CAT) scans, magnetic resonance imaging (MRI), and ultrasound technologies has allowed doctors to noninvasively examine the inside of the body. Improved radiation therapy is used to fight cancer. Lasers have been applied to eye surgery and other types of surgery that require extremely fine control.

The first successful organ transplant occurred in 1954 in Boston when a patient received the kidney of his twin brother and lived for another eight years. Improved surgical techniques and the development of antirejection drugs have created a situation in which the transplantation of hearts, livers, kidneys, blood vessels, bone marrow, corneas, and other organs or tissues is now commonplace in developed countries.

International cooperation in health care, fostered by private foundations and organizations like the World Health Organization (WHO), has led to considerable successes in delivering basic health and sanitation care to developing countries. The worldwide smallpox vaccination campaign, led by WHO, eradicated that dreaded disease in 1979, except for a few samples retained in government laboratories. Jonas Salk (1914–1995) and Albert Sabin (1906–1993) both created polio vaccines in the 1950s, ending a scourge that crippled children. WHO has targeted polio as the next disease to be eradicated through worldwide vaccination.

The evolutionary struggle between humanity and pathogens has led to exotic new threats, such as acquired immunodeficiency syndrome (AIDS), Ebola, and Lassa fever. Creutzfeldt-Jakob disease (related to mad cow disease and scrapie in animals) is in a class of its own, in that it is apparently caused by prions, pathogens the size of a molecule. The overuse of antibiotics in developed countries eventually led to the evolution of new antibiotic-resistant strains of bacteria. In the United States, nonprescription antibiotics could be purchased up until the 1950s, and many countries still have no effective control over the purchase of antibiotics. The rise of multiple-drug resistant bacteria has brought back diseases, such as tuberculosis, that doctors had thought remained only among the poor and negligent. The new antibiotic-resistant strains of diseases are an excellent example of Darwinist natural selection in action, and have led to efforts by physicians to reduce the use of antibiotics when not warranted.

The physiologist Robert Edwards (1925–) and gynecologist Patrick Steptoe (1913–1988) developed in vitro fertilization, a medical technique for removing a mature egg from a woman, fertilizing it with donor sperm in the laboratory, allowing it to divide several times until it becomes a blastocyst, and implanting the blastocyst in a uterus. The patient Lesley Brown was impregnated with her own egg fertilized by her husband’s sperm. On July 25, 1978, a daughter named Louise Joy was delivered by caesarian section, becoming the world’s first “test-tube baby.” In vitro fertilization and other assisted reproductive technologies have raised new ethical issues and laid the essential groundwork for the possible future genetic engineering of children.

Advances in genetics and the Human Genome Project increased our understanding in all areas of medicine. In 1989, the team led by Lap-Chee Tsui (1950–) discovered the gene that caused the genetic disorder cystic fibrosis, a necessary first step to eventually overcoming that disease. The study of the immune system has led to new therapies and ways to combat autoimmune diseases. The issue of cloning, long a staple of science fiction, became a very real problem in the 1990s when animals were successfully cloned. The new field of bioethics has been created to deal with the difficult ethical and moral issues that medical advances have created.

See also Acquired Immunodeficiency Syndrome; Bioethics; Birth Control Pill; Carson, Rachel; Centers for Disease Control and Prevention; Cloning; Edelman, Gerald M.; Edwards, Robert; Elion, Gertrude B.; Genetics; Human Genome Project; In Vitro Fertilization; Kübler-Ross, Elisabeth; Lasers; Levi-Montalcini, Rita; Medawar, Peter; Microbiology; National Institutes of Health; Neuroscience; Organ Transplants; Pharmacology; Population Studies; Prions; Psychology; Sabin, Albert; Salk, Jonas; Selye, Hans; Smallpox Vaccination Campaign; Steptoe, Patrick; Tsui, Lap-Chee; World Health Organization; Yalow, Rosalyn