HIV/AIDS
Acquired immunodeficiency syndrome, or AIDS, is the final, life-threatening stage of infection with any of the human immunodeficiency viruses (HIV-1, its many subtypes, or HIV-2), a condition in humans in which the immune system begins to fail, leading to life-threatening infections. HIV is transmitted from person to person sexually (including via anal, oral, and vaginal intercourse, both heterosexually and homosexually), through contact with blood (mainly via equipment used to inject illicit drugs and, rarely, via medical uses of blood), and perinatally (from mother to fetus or newborn during pregnancy, labor, and delivery, or after birth through breast-feeding).
Epidemiology
HIV-1 has spread worldwide, infecting more than 36 million people by 2001. HIV-2, which seems to be less clinically severe and possibly less transmissible from person to person, has mainly been a public health problem for West African nations. Originally epidemic in African and urban settings, HIV and AIDS are now among the most common serious infections globally, including in the Americas and Eurasia and in rural settings. All ages, racial and ethnic groups, and persons of all sexual orientations have been infected.
Symptoms, Diagnosis, and Treatment
Persons initially infected with HIV may develop an "acute retroviral syndrome" characterized by fever, lymph node enlargement, and flu-like symptoms. If symptoms are present, they clear spontaneously, but all infected persons, both with and without symptoms, remain infected and infectious to others indefinitely. The incubation period is highly variable, averaging about a decade, but ranging from a few months or years to possibly longer than two decades. When sufficient damage to the immune system has been sustained, measured either by laboratory cell counts of the helperT cells or by onset of opportunistic infections, the patient is said to have AIDS. Common manifestations of HIV infection include tiredness, lymph node enlargement, fever, weight loss, and yeast infections of the mouth and vagina.
HIV infection is diagnosed by laboratory detection of evidence of infection, usually identification of HIV-specific antibodies in a blood, oral fluid, or urine specimen. AIDS can be diagnosed in HIV-infected persons in several ways, based on either laboratory evidence of immunodeficiency (lowered levels of CD4+ cells), or clinically by onset of any one or more of a specific list of opportunistic diseases. Opportunistic diseases are those that occur only, or most severely, in patients whose immune systems are impaired. The most common opportunistic diseases in AIDS patients are Pneumocystis carinii pneumonia, Kaposi's sarcoma, toxoplasmosis of the brain, tuberculosis and other mycobacterial infections, and severe herpes, cytomegalo virus, and yeast infections.
As of 2001, all of the more than seventeen antiviral drugs used to treat HIV infection act by interfering with one of the enzymes that HIV needs to complete its life cycle. No treatments result in a cure for HIV infection. The antiviral drugs prevent HIV from growing and further damaging the host's immune system. Thus, the goal of treatment is to preserve the patient's health. Patients must take several antiviral drugs daily. Research on more and better antiviral drugs, and on methods to reconstitute the impaired immune system, is ongoing. A key part of treatment is the prevention of opportunistic infections with specific vaccines and antibiotics.
Prevention
Prevention of HIV infections is deceptively simple: Refrain from having sexual contact and from sharing drug-injecting paraphernalia with anyone who is infected. However, the rapid and continuing global spread of HIV, despite its well-known and severe clinical consequences, points out how difficult it is to change risky sexual and drug-taking behaviors. Many successful educational and social interventions have been demonstrated, but sustaining them in large populations for long periods requires extensive resources and a strong public health commitment.
Condoms, even when used correctly and 100 percent of the time during sexual activity, are ultimately an unreliable prevention against the transmission of HIV. The most recent and best studies show that condoms only provide protection against the HIV virus during vaginal intercourse 85 percent of the time. With anal intercourse, the condom prevention rate drops to only about 50 percent. To date, there is no evidence showing condoms offer any prevention when used during oral sex.
The research effort to develop a vaccine to prevent HIV infection has been intense, but the biologic obstacles to success are immense and unprecedented. Because HIV permanently infects cells of the immune system, infection of a single cell results in lifelong infection for the host. Thus, a completely effective vaccine would need to prevent even a single cell from becoming infected. No such vaccine exists for any infection, so HIV will require a new vaccine paradigm. Possible lines of research include stimulating the immune system to detect and eliminate HIV-infected cells, or genetically transforming the HIV in an infected person so as to render it nonvirulent.
Further information on HIV and AIDS is widely available in many user-friendly and scholarly formats. The Internet is a rich source of information, with sites sponsored by public health agencies, such as the Joint United Nations Programme on HIV/AIDS (http://www.unaids.org) and the Centers for Disease Control and Prevention (http://www.cdc.gov), which are particularly recommended. Several texts, popular books, and scholarly journals have been devoted exclusively to AIDS public health issues and scientific research. The first of December has been designated World AIDS Day, and many governments, schools, and organizations sponsor community and educational events to coincide with that date each year.5
Bibliography
Feldman, E. A., and Bayer, R. (1999). Blood Feuds: AIDS, Blood, and the Politics of Medical Disaster. New York: Oxford University Press.
Garrett, L. (1994). The Coming Plague: Newly Emerging Diseases in a World Out of Balance. New York: Farrar, Straus and Giroux.
Mann, J. M.; Tarantola, D.; and the Global AIDS Policy Coalition, eds. (1998). AIDS in the World II/Global Dimensions, Social Roots, and Responses. New York: Oxford University Press.
Shilts, R. (1987). And the Band Played On: Politics, People, and the AIDS Epidemic. New York: St. Martin's Press.
5 Adapted from "AIDS." Answers.com. Encyclopedia of Public Health, The Gale Group, Inc, 2002. http://www.answers.com/topic/aids, accessed January 22, 2007.