Characteristics
Beginning in the late 1970s, physicians in New York and California reported increasing incidence of a rare cancer, Kaposi’s sarcoma, and a variety of infections including pneumocystis pneumonia among previously healthy young homosexual men. Because of the unusual character of these diseases, which are typically associated with failure of the immune system, epidemiologists began seeking clues that might link these cases.In 1983, in French and American laboratories, an unknown human retrovirus was identified and named HIV-1 for “human immunodeficiency virus.” Although the biological and geographic origins of the organism remain obscure, the AIDS epidemic appears to mark the first time it has spread widely in human populations. No evidence exists for casual transmission of HIV. Following identification of HIV-1, tests to detect antibodies against it were devised in 1984. Although these tests do not detect the virus itself, they are generally effective in identifying infection because high levels of antibody are produced in most infected individuals.
The enzyme-linked immunosorbent assay (ELISA), followed by Western blot testing, has enabled the screening of donated blood to protect the blood supply from HIV, as well as testing for epidemiological and diagnostic purposes. As HIV infection precedes the development of AIDS, often by several years, the precise parameters of the epidemic have been difficult to define. Although “cofactors” that may determine the onset of symptoms remain unknown, evidence suggests that HIV-infected individuals will eventually develop AIDS.
Researchers have identified three epidemiological patterns of HIV transmission, which roughly follow geographic boundaries. Pattern I includes North America, Western Europe, Australia, New Zealand, and many urban centers in Latin America. In these industrial, highly developed areas, transmission has been predominantly among homosexual and bisexual men. Since the introduction of widespread blood screening, transmission via blood in these areas now occurs principally among intravenous drug users who share injection equipment. Although little evidence exists of widespread infection among heterosexuals in these countries, heterosexual transmission from those infected intravenously has increased, leading to a rise in pediatric cases resulting from perinatal transmission. Within the United States, distribution of AIDS has been marked by disproportionate representation of minorities and the poor.
As the principal mode of transmission has shifted to intravenous drug use, AIDS has increasingly become an affliction of the urban underclass. Surveys reveal that 50 percent or more of intravenous drug users in New York City are infected with HIV. Women are typically infected by intravenous drug use or by sexual contact with a drug user. In pattern II countries, comprised of sub-Saharan Africa and, increasingly, Latin America, transmission of HIV occurs predominantly through heterosexual contact. In some urban areas in these countries, up to 25 percent of all sexually active adults are reported to be infected, and a majority of female prostitutes are seropositive.
Transfusion remains a mode of transmission because universal blood screening is not routine. Unsterile injections and medical procedures may also contribute to the spread of infection. In these areas, perinatal transmission is an important aspect of the epidemic. Pattern III countries, including North Africa, the Middle East, Eastern Europe, Asia, and the Pacific, initially experienced less morbidity and mortality from the pandemic. Apparently, HIV-1 was not present in these areas until the mid-1980s.
The nature of world travel, however, has diminished the significance of geographic isolation as a means of protecting a population from contact with a pathogen. In 1985, a related virus, HIV-2, was discovered in West Africa. Although early reports suggested that HIV-2 is less pathogenic, the natural history of this agent remains unclear, as does its prevalence. HIV cripples the body’s immunologic system, making an infected individual vulnerable to other disease-causing agents in the environment.
The most common of these opportunistic infections in AIDS patients has been pneumocystis pneumonia, previously seen principally in patients receiving immunosuppressive drugs. In addition to pneumocystis, AIDS patients are prone to other infectious agents such as cytomegalovirus, Candida albicans (a yeastlike fungus), and Toxoplasma gondii (a protozoan parasite). Moreover, a resurgence of tuberculosis has been reported in nations with high AIDS incidence. Immunologic damage occurs by depletion of a specific type of white blood cell called a helper T4 lymphocyte.
Destruction of these cells accounts for the vulnerability to normally harmless infectious agents. In some cases, infection of the central nervous system with HIV may cause damage to the brain and spinal column, resulting in severe cognitive and motor dysfunction. In its late manif estations, AIDS causes severe wasting. Death may occur from infection, functional failure of the central nervous system, or starvation. HIV infection has a wide spectrum of clinical manifestations. After infection, an individual may remain free of symptoms for years, even a decade or longer. Some individuals experience fever, rash, and malaise at the time of infection when antibodies are first produced. Patients commonly present with general lymphadenopathy, weight loss, diarrhea, or an opportunistic infection. Diagnosis is confirmed by finding antibodies for HIV or by a decline in T4 cells.
Most experts now agree that HIV infection itself be considered a disease, regardless of symptoms. Because the virus becomes encoded within the genetic material of the host cell and is highly mutable, the problem of finding safe and effective therapies has been extremely difficult. Studies have attempted to determine the antiHIV properties of many drugs, but the ethical and economic obstacles to clinical trials with experimental drugs are formidable.
Given the immediacy of the epidemic, it is difficult to structure appropriate randomized clinical trials, which often take considerable time, to assess the safety and efficacy of a drug. Since the beginning of the epidemic, clinical research has refined the treatment of opportunistic infections.
History
In its first decade, AIDS created considerable suffering and generated an ongoing worldwide health crisis.During this brief period, the epidemic was identified and characterized epidemiologically, basic modes of transmission specified, a causal organism isolated, and effective tests for infection developed. In spite of this remarkable progress, which required the application of sophisticated epidemiological, clinical, and scientific research, the barriers to controlling AIDS are imposing and relate to the most complex biomedical and political questions. AIDS has already sorely tested the capabilities of research, clinical, and public-health institutions throughout the world. Because HIV is related to other recently isolated primate retroviruses, such as simian T lymphotropic virus (STLV) -III in African green monkeys, many have speculated that HIV originated in Africa.Antibodies to HIV were discovered in stored blood dating back to 1959 in Zaire. According to experts, it is likely that HIV has existed for many years in isolated groups in central Africa. Because outside contacts were minimal, the virus rarely spread, and epidemics could not be sustained. Once a sizable reservoir of infection was established, however, HIV became pandemic. As with other sexually transmitted diseases, such as syphilis, no country wished the stigma of association with the virus’s “origin.” The epidemic began at a moment of relative complacency, especially in the developed world, concerning epidemic infectious disease. Not since the influenza of 1918–20 had an epidemic appeared with such devastating potential.
The developed world had experienced a health transition from infectious to chronic disease and had focused its resources and attention on systemic, noninfectious ailments. Thus, AIDS appeared at a historical moment comprising little social or political experience in confronting such a public-health crisis. The epidemic fractured a widely held belief in medical security. Not surprisingly, early sociopolitical responses were characterized by denial. Initial theories, when few cases had been reported, centered on aspects of “fast-track” gay sexual culture that might explain the outbreak of immune-compromised men.
Additional cases among blood recipients, however, soon led the U.S. Centers for Disease Control and Prevention to the conclusion that an infectious agent was the likely link. Nevertheless, in the earliest years of the epidemic, few wished to confront openly the possibility of spread beyond the specified “high-risk” groups. During this period, when government interest and funding lagged, grassroots organizations, especially in the homosexual community, were created to meet the growing need for education, counseling, patient services, and – in some instances – clinical research. Such groups worked to overcome the denial, prejudice, and bureaucratic inertia that limited governmental response.
As the nature and extent of the epidemic became clearer, however, hysteria sometimes replaced denial. Because the disease was powerfully associated with behaviors identified as immoral or illegal (or both), the stigma of those infected was heightened. Victims were often divided into categories: those who acquired their infections through transfusions or perinatally, the “innocent victims”; and those who engaged in high-risk, morally condemnable behaviors, the “guilty perpetrators” of disease. Since the early recognition of behavioral risks for infection, there has been a tendency to blame those who became infected through drug use or homosexuality, behaviors viewed as “voluntary.” Some religious groups in the United States and elsewhere saw the epidemic as an occasion to reiterate particular moral views about sexual behavior, drug use, sin, and disease.
AIDS was viewed as “proof” of a certain moral order. AIDS victims have been subjected to a range of discriminatory behavior, including loss of employment, housing, and insurance. Since the onset of the epidemic, violence against gays in the United States has increased. Despite the well-documented modes of H IV transmission, fears of casual transmission persist. In some communities, parents protested when HIV-infected schoolchildren were permitted to attend school. In one instance, a family with an HIV-infected child was driven from a town by the burning of their home. By 1983, as potential ramifications of the epidemic became evident, national and international scientific and public-health institutions began to mobilize. In the United States, congressional appropriations for research and education began to rise significantly.
The National Academy of Sciences issued a consensus report on the epidemic in 1986. A presidential commission held public hearings and eventually issued a report calling for protection of AIDS sufferers against discrimination and a more extensive federal commitment to drug treatment. The World Health Organization (WHO) established a Global Program on AIDS in 1986 to coordinate international efforts in epidemiological surveillance, education, prevention, and research.
Despite growing recognition of the epidemic’s significance, considerable debate continued over the most effective public-health responses. Although some nations – such as Cuba – experimented with programs mandating isolation of HIV-infected individuals, the World Health Organization lobbied against coercive measures. Given the lifelong nature of HIV infection, effective isolation would require lifetime incarceration. With the available variety of less restrictive measures, most nations rejected quarantine as both unduly coercive and unlikely to achieve control.
Traditional publichealth approaches to communicable disease, including contact tracing and mandatory treatment, have less potential for control because no means exist to render an infected individual noninfectious. Because biomedical technologies to prevent transmission appear to be some years away, the principal public-health approaches to controlling the pandemic rest on education and behavior modification.
Heightened awareness of the dangers of unprotected anal intercourse among gay men, for example, has led to a significant decline in new infections among this population. Nevertheless, as many public-health officials have noted, encouraging the modification of risk behaviors, especially those relating to sexuality and drug abuse, presents no simple task, even in the face of a dread disease. In the developing world, AIDS threatens to reverse recent advances in infant and child survival.
The epidemic is likely to have a substantial impact on demographic patterns. Because the disease principally affects young and middle-aged adults (ages 20–49), it has already had tragic social and cultural repercussions. Transmitted both horizontally (via sexual contact) and vertically (from mother to infant), it has the potential to depress the growth rate of human populations, especially in areas of the developing world. In this respect, the disease could destabilize the work force and depress local economies.
AIDS has clearly demonstrated the complex relationship of biological and behavioral forces in determining patterns of health and disease. Altering the course of the epidemic by human design has already proved to be no easy matter. The lifelong infectiousness of carriers; the private, biopsychosocial nature of sexual behavior and drug abuse; and the stigma already attached to those at greatest risk – all have made effective public policy intervention even more difficult. Finally, the very nature of the virus itself – its complex and mutagenic nature – makes a short-term technological breakthrough unlikely.
The remarkable progress in understanding AIDS is testimony to the sophistication of contemporary bioscience; the epidemic, however, is also a sobering reminder of the limits of that science. Any historical assessment of the AIDS epidemic must be considered provisional. Nevertheless, it is already clear that AIDS has forced us to confront a new set of biological imperatives.
Allan M. Brandt
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