AIDS Acquired Immunodeficiency Syndrome (AIDS), human viral disease that ravages the immune system, undermining the body’s ability to defend itself from infection and disease. Caused by the human immunodeficiency virus (HIV), AIDS leaves an infected person vulnerable to opportunistic infections. Such infections are harmless in healthy people, but in those whose immune systems have been greatly weakened, they can prove fatal. Although there is no cure for AIDS, new drugs are available that can prolong the life spans and improve the quality of life of infected people. Human Immunodeficiency Virus The human immunodeficiency virus (HIV), which causes acquired immunodeficiency syndrome (AIDS), principally attacks CD4 T-cells, a vital part of the human immune system. As a result, the body’s ability to resist opportunistic viral, bacterial, fungal, protozoal, and other infection is greatly weakened. Pneumocystis carinii pneumonia is the leading cause of death among people with HIV infection, but the incidence of certain types of cancers such as B-cell lymphomas and Kaposi’s sarcoma is also increased. Neurological complications and dramatic weight loss, or “wasting,” are characteristic of endstage HIV disease (AIDS). HIV can be transmitted sexually; through contact with contaminated blood, tissue, or needles; and from mother to child during birth or breastfeeding. Full-blown symptoms of AIDS may not develop for more than 10 years after infection. Infection with HIV does not necessarily mean that a person has AIDS. Some people who have HIV infection may not develop any of the clinical illnesses that define the full-blown disease of AIDS for ten years or more. Physicians prefer to use the term AIDS for cases where a person has reached the final, life-threatening stage of HIV infection. PREVALENCE AIDS was first identified in 1981 among homosexual men and intravenous drug users in New York and California. Shortly after its detection in the United States, evidence of AIDS epidemics grew among heterosexual men, women, and children in sub-Saharan Africa. AIDS quickly developed into a worldwide epidemic, affecting virtually every nation. By 2002 an estimated 38.6 million adults and 3.2 million children worldwide were living with HIV infection or AIDS. The World Health Organization (WHO), a specialized agency of the United Nations (UN), estimates that from 1981 to the end of 2002 about 20 million people died as a result of AIDS. About 4.5 million of those who died were children under the age of 15. CAUSE AIDS is the final stage of a chronic infection with the human immunodeficiency virus. There are two types of this virus: HIV-1, which is the primary cause of AIDS worldwide, and HIV-2, found mostly in West Africa. On its surface, HIV carries a protein structure that recognizes and binds only with a specific structure found on the outer surface of certain cells. HIV attacks any cell that has this binding structure. However, white blood cells of the immune system known as T cells, which orchestrate a wide variety of disease-fighting mechanisms, are especially vulnerable to HIV attack. Particularly vulnerable are certain T cells known as CD4 cells. When HIV infects a CD4 cell, it commandeers the genetic tools within the cell to manufacture new HIV virus. The newly formed HIV virus then leaves the cell, destroying the CD4 cell in the process. No existing medical treatment can completely eradicate HIV from the body once it has integrated into human cells. The loss of CD4 cells endangers health because these immune cells help other types of immune cells respond to invading organisms. The average healthy person has over 1,000 CD4 cells per microliter of blood. In a person infected with HIV, the virus steadily destroys CD4 cells over a period of years, diminishing the cells’ protective ability and weakening the immune system. When the density of CD4 cells drops to 200 cells per microliter of blood, the infected person becomes vulnerable to any of about 26 opportunistic infections and rare cancers, which take advantage of the weakened immune defenses to cause disease. HOW HIV INFECTION SPREADS Scientists have identified three ways that HIV infections spread: sexual intercourse with an infected person, contact with contaminated blood, and transmission from an infected mother to her child before or during birth or through breastfeeding. A Sex with an Infected Person HIV transmission occurs most commonly during intimate sexual contact with an infected person, including genital, anal, and oral sex. The virus is present in the infected person’s semen or vaginal fluids. During sexual intercourse, the virus gains access to the bloodstream of the uninfected person by passing through openings in the mucous membrane—the protective tissue layer that lines the mouth, vagina, and rectum—and through breaks in the skin of the penis. In the United States and Canada, HIV is most commonly transmitted during sex between homosexual men, but the incidence of HIV transmission between heterosexual men and women has rapidly increased. In most other parts of the world, HIV is most commonly transmitted through heterosexual sex. B Contact with Infected Blood Direct contact with HIV-infected blood occurs when people who use heroin or other injected drugs share hypodermic needles or syringes contaminated with infected blood. Sharing of contaminated needles among intravenous drug users is the primary cause of HIV infection in eastern Europe, particularly in Ukraine, Russia, Belarus, and Moldova. Epidemics of HIV infection among drug users have also emerged in Georgia, Armenia, Azerbaijan, and Kazakhstan in Central Asia. Less frequently, HIV infection results when health professionals accidentally stick themselves with needles containing HIV-infected blood or expose an open cut to contaminated blood. Some cases of HIV transmission from transfusions of infected blood, blood components, and organ donations were reported in the 1980s. Since 1985 government regulations in the United States and Canada have required that all donated blood and body tissues be screened for the presence of HIV before being used in medical procedures. As a result of these regulations, HIV transmission caused by contaminated blood transfusion or organ donations is rare in North America. However, the problem continues to concern health officials in sub-Saharan Africa. Less than half of the 46 nations in this region have blood-screening policies. By some estimates only 25 percent of blood transfusions are screened for the presence of HIV. WHO hopes to establish blood safety programs in more than 80 percent of sub-Saharan countries by 2003. C Mother-to-Child Transmission HIV can be transmitted from an infected mother to her baby while the baby is still in the woman’s uterus or, more commonly, during childbirth. The virus can also be transmitted through the mother’s breast milk during breastfeeding. Mother-to-child transmission accounts for 90 percent of all cases of AIDS in children. Mother-to-child transmission is particularly prevalent in Africa, where the number of women infected with HIV is ten times the rate found in other regions. Studies conducted in several cities in southern Africa in 1998 indicate that up to 45 percent of pregnant women in these cities carry HIV. D Misperceptions About HIV Transmission The routes of HIV transmission are well documented by scientists, but health officials continually grapple with the public’s unfounded fears concerning the potential for HIV transmission by other means. HIV differs from other infectious viruses in that it dies quickly if exposed to the environment. No evidence has linked HIV transmission to casual contact with an infected person, such as a handshake, hugging, or kissing, or even sharing dishes or bathroom facilities. Studies have been unable to identify HIV transmission from modes common to other infectious diseases, such as an insect bite or inhaling virus-infected droplets from an infected person’s sneeze or cough. SYMPTOMS Without medical intervention, AIDS progresses along a typical course. Within one to three weeks after infection with HIV, most people experience flu-like symptoms, such as fever, sore throat, headache, skin rash, tender lymph nodes, and a vague feeling of discomfort. These symptoms last one to four weeks. During this phase, known as acute retroviral syndrome, HIV reproduces rapidly in the blood. The virus circulates in the blood throughout the body, particularly concentrating in organs of the lymphatic system. The normal immune defenses against viral infections eventually activate to battle HIV in the body, reducing but not eliminating HIV in the blood. Infected individuals typically enter a prolonged asymptomatic phase, a symptom-free period that can last ten years or more. While persons who have HIV may remain in good health during this period, HIV continues to replicate, progressively destroying the immune system. Often an infected person remains unaware that he or she carries HIV and unknowingly transmits the virus to others during this phase of the infection. When HIV infection reduces the number of CD4 cells to around 200 per microliter of blood, the infected individual enters an early symptomatic phase that may last a few months to several years. HIV-infected persons in this stage may experience a variety of symptoms that are not life-threatening but may be debilitating. These symptoms include extensive weight loss and fatigue (wasting syndrome), periodic fever, recurring diarrhea, and thrush, a fungal mouth infection. An early symptom of HIV infection in women is a recurring vaginal yeast infection. Unlike earlier stages of the disease, in this early symptomatic phase the symptoms that develop are severe enough to cause people to seek medical treatment. Many may first learn of their infection in this phase. DIAGNOSING AIDS Physicians prefer to differentiate between people who have HIV infection and those who have AIDS. The Centers for Disease Control and Prevention (CDC), based in Atlanta, Georgia, recommends that physicians reserve the diagnosis of AIDS for HIV-infected individuals whose CD4 count falls below 200 cells per microliter of blood. A diagnosis of AIDS can also be made without confirmation of CD4 levels if someone who has no other reason for immune system damage develops an opportunistic disease. TREATMENT While no medical treatment cures AIDS, in the relatively short time since the disease was first recognized, new methods to treat the disease have developed rapidly. Health-care professionals focus on three areas of therapy for people living with HIV infection or AIDS: antiretroviral therapy using drugs that suppress HIV replication; medications and other treatments that fight the opportunistic infections and cancers that commonly accompany HIV infection; and support mechanisms that help people deal with the emotional repercussions as well as the practical considerations of living with a disabling, potentially fatal disease. PREVENTION With a vaccine for AIDS years away and no cure on the horizon, experts believe that the most effective treatment for AIDS is to prevent the occurrence of HIV infection. Health officials focus public education programs on altering risky behaviors linked to HIV transmission, particularly unsafe sexual practices and needle-sharing by intravenous drug users. Safe-sex campaigns sponsored by health clinics, social centers, schools, and churches encourage sexual abstinence or monogamy (sexual relations with only one partner). Education programs instruct about the proper way to use condoms to provide a protective barrier against transmission of HIV during sexual intercourse. Needle-exchange programs, which provide clean needles to drug users, enable intravenous drug abusers to avoid sharing HIV-contaminated needles. Needle-exchange programs have been widely criticized because they seem to condone illicit drug use. However, numerous U.S. government-funded studies have indicated that such programs reduce HIV transmission without promoting greater drug use. To reduce the accidental transmission of HIV during medical procedures, both the United States and Canada have established strict guidelines for health-care settings, including the use of protective clothing and proper instrument disposal. In the United States, the effectiveness of public education programs that target people at risk for HIV infection was well demonstrated in the gay community of San Francisco, California, in the 1980s. In 1982 and 1983, 6,000 to 8,000 people in San Francisco became infected with HIV. The gay community rallied to promote condom use and advocate monogamy through extensive education programs and public health advertisements geared for gay men. These public education programs were credited with reducing the number of gay men in San Francisco who became HIV infected. By 1993 the number of new infections declined to 1,000, and by 1999, fewer than 500 people were infected each year. Public education about AIDS has also proven effective in other countries. Uganda was one of the first African countries to report cases of HIV infection. The first cases of AIDS were reported there in 1982, and by the late 1980s Uganda had one of the highest rates of HIV infection in the world. The Ugandan government was one of the first countries to set up a partnership with WHO to create a national AIDS control program called the AIDS Information Centre (AIC). The AIC has established extensive education programs promoting condom use and other methods to prevent HIV from spreading further. The program has also worked with community organizations to change social behaviors that increase the risk of HIV infection. The AIC promotes its message using innovative drama, song, and dance programs, a particularly effective communication method for African communities. AIC established confidential HIV testing services that provide same-day results and community counseling programs. As a result of Uganda’s quick response to the AIDS epidemic, the number of HIV infected people in that country has declined significantly since 1993, during a time when most other African nations faced a frightening increase in the incidence of HIV infection. Public health officials have learned that education programs that teach and reinforce safe behaviors through a series of meetings are more effective than one-time exposure to public-health information provided in a class lecture, magazine article, advertisement, or pamphlet. Education programs tailored to reflect specific ethnic and cultural preferences prove even more effective. For example, the Canadian Aboriginal AIDS Network creates HIV education programs that fight the common misperception among the indigenous peoples of Canada that AIDS is primarily a disease of white, affluent people. Among indigenous communities, the network promotes programs that use colloquial language to increase awareness about safe sex practices and needle use.
