AIDS

2007 Schools Wikipedia Selection. Related subjects: Health and medicine

Acquired Immunodeficiency Syndrome (AIDS)
Classifications and external resources

The Red ribbon is a symbol for solidarity with HIV-positive people and those living with AIDS.
ICD- 10	B 24.
ICD- 9	042
DiseasesDB	5938
MedlinePlus	000594
eMedicine	emerg/253

Acquired Immune Deficiency Syndrome (AIDS or Aids) is a collection of symptoms and infections in humans resulting from the specific damage to the immune system caused by the human immunodeficiency virus (HIV). The late stage of the condition leaves individuals prone to opportunistic infections and tumors. Although treatments for AIDS and HIV exist to slow the virus's progression, there is no known cure. HIV is transmitted through direct contact of a mucous membrane or the bloodstream with a bodily fluid containing HIV, such as blood, semen, vaginal fluid, preseminal fluid, and breast milk. This transmission can come in the form of anal, vaginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth, or breastfeeding, or other exposure to one of the above bodily fluids.

Most researchers believe that HIV originated in sub-Saharan Africa during the twentieth century; it is now a pandemic, with an estimated 38.6 million people now living with the disease worldwide. As of January 2006, the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) estimate that AIDS has killed more than 25 million people since it was first recognized on June 5, 1981, making it one of the most destructive epidemics in recorded history. In 2005 alone, AIDS claimed an estimated 2.4–3.3 million lives, of which more than 570,000 were children. A third of these deaths are occurring in sub-Saharan Africa, retarding economic growth and destroying human capital. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but routine access to antiretroviral medication is not available in all countries. HIV/AIDS stigma is more severe than that associated with other life-threatening conditions and extends beyond the disease itself to providers and even volunteers involved with the care of people living with HIV.

Infection by HIV

AIDS is the most severe manifestation of infection with HIV. HIV is a retrovirus that primarily infects vital components of the human immune system such as CD4⁺ T cells (a subset of T cells), macrophages and dendritic cells. It directly and indirectly destroys CD4⁺ T cells. CD4⁺ T cells are required for the proper functioning of the immune system. When HIV kills CD4⁺ T cells so that there are fewer than 200 CD4⁺ T cells per microliter (µL) of blood, cellular immunity is lost, leading to the condition known as AIDS. Acute HIV infection progresses over time to clinical latent HIV infection and then to early symptomatic HIV infection and later, to AIDS, which is identified on the basis of the amount of CD4⁺ T cells in the blood and the presence of certain infections.

In the absence of antiretroviral therapy, the median time of progression from HIV infection to AIDS is nine to ten years, and the median survival time after developing AIDS is only 9.2 months. However, the rate of clinical disease progression varies widely between individuals, from two weeks up to 20 years. Many factors affect the rate of progression. These include factors that influence the body's ability to defend against HIV such as the infected person's general immune function. Older people have weaker immune systems, and therefore have a greater risk of rapid disease progression than younger people. Poor access to health care and the existence of coexisting infections such as tuberculosis also may predispose people to faster disease progression. The infected person's genetic inheritance plays an important role and some people are resistant to certain strains of HIV. An example of this is people with the CCR5-Δ32 mutation are resistant to infection with certain strains of HIV. HIV is genetically variable and exists as different strains, which cause different rates of clinical disease progression. The use of highly active antiretroviral therapy prolongs both the median time of progression to AIDS and the median survival time.

Diagnosis

Since June 5, 1981, many definitions have been developed for epidemiological surveillance such as the Bangui definition and the 1994 expanded World Health Organization AIDS case definition. However, clinical staging of patients was not an intended use for these systems as they are neither sensitive, nor specific. In developing countries, the World Health Organization staging system for HIV infection and disease, using clinical and laboratory data, is used and in developed countries, the Centers for Disease Control (CDC) Classification System is used.

WHO disease staging system for HIV infection and disease

In 1990, the World Health Organization (WHO) grouped these infections and conditions together by introducing a staging system for patients infected with HIV-1. An update took place in September 2005. Most of these conditions are opportunistic infections that are easily treatable in healthy people.

Stage I: HIV disease is asymptomatic and not categorized as AIDS

Stage II: includes minor mucocutaneous manifestations and recurrent upper respiratory tract infections

Stage III: includes unexplained chronic diarrhea for longer than a month, severe bacterial infections and pulmonary tuberculosis

Stage IV: includes toxoplasmosis of the brain, candidiasis of the esophagus, trachea, bronchi or lungs and Kaposi's sarcoma; these diseases are indicators of AIDS.

CDC classification system for HIV infection

The Centers for Disease Control and Prevention (CDC) originally classified AIDS as GRID which stood for Gay Related Immune Disease. However, after determining that AIDS is not isolated to homosexual people the name was changed to the neutral AIDS. In 1993, the CDC expanded their definition of AIDS to include all HIV positive people with a CD4⁺ T cell count below 200 per µL of blood or 14% of all lymphocytes. The majority of new AIDS cases in developed countries use either this definition or the pre-1993 CDC definition. The AIDS diagnosis still stands even if, after treatment, the CD4⁺ T cell count rises to above 200 per µL of blood or other AIDS-defining illnesses are cured.

HIV test

Many people are unaware that they are infected with HIV. Less than 1% of the sexually active urban population in Africa has been tested, and this proportion is even lower in rural populations. Furthermore, only 0.5% of pregnant women attending urban health facilities are counseled, tested or receive their test results. Again, this proportion is even lower in rural health facilities. Therefore, donor blood and blood products used in medicine and medical research are screened for HIV. Typical HIV tests, including the HIV enzyme immunoassay and the Western blot assay, detect HIV antibodies in serum, plasma, oral fluid, dried blood spot or urine of patients. However, the window period (the time between initial infection and the development of detectable antibodies against the infection) can vary. This is why it can take 3-6 months to seroconvert and test positive. Commercially available tests to detect other HIV antigens, HIV- RNA, and HIV-DNA in order to detect HIV infection prior to the development of detectable antibodies are available. For the diagnosis of HIV infection these assays are not specifically approved, but are nonetheless routinely used in developed countries.

Symptoms and complications

The symptoms of AIDS are primarily the result of conditions that do not normally develop in individuals with healthy immune systems. Most of these conditions are infections caused by bacteria, viruses, fungi and parasites that are normally controlled by the elements of the immune system that HIV damages. Opportunistic infections are common in people with AIDS. HIV affects nearly every organ system. People with AIDS also have an increased risk of developing various cancers such as Kaposi's sarcoma, cervical cancer and cancers of the immune system known as lymphomas.

Additionally, people with AIDS often have systemic symptoms of infection like fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss. After the diagnosis of AIDS is made, the current average survival time with antiretroviral therapy ( as of 2005) is estimated to be more than 5 years, but because new treatments continue to be developed and because HIV continues to evolve resistance to treatments, estimates of survival time are likely to continue to change. Without antiretroviral therapy, death normally occurs within a year. Most patients die from opportunistic infections or malignancies associated with the progressive failure of the immune system.

The rate of clinical disease progression varies widely between individuals and has been shown to be affected by many factors such as host susceptibility and immune function health care and co-infections, as well as factors relating to the viral strain. The specific opportunistic infections that AIDS patients develop depend in part on the prevalence of these infections in the geographic area in which the patient lives.

Major pulmonary illnesses

• Pneumocystis jiroveci pneumonia (originally known as Pneumocystis carinii pneumonia, often-abbreviated PCP) is relatively rare in healthy, immunocompetent people, but common among HIV-infected individuals. Before the advent of effective diagnosis, treatment and routine prophylaxis in Western countries, it was a common immediate cause of death. In developing countries, it is still one of the first indications of AIDS in untested individuals, although it does not generally occur unless the CD4 count is less than 200 per µL.
• Tuberculosis (TB) is unique among infections associated with HIV because it is transmissible to immunocompetent people via the respiratory route, is easily treatable once identified, may occur in early-stage HIV disease, and is preventable with drug therapy. However, multidrug resistance is a potentially serious problem. Even though its incidence has declined because of the use of directly observed therapy and other improved practices in Western countries, this is not the case in developing countries where HIV is most prevalent. In early-stage HIV infection (CD4 count >300 cells per µL), TB typically presents as a pulmonary disease. In advanced HIV infection, TB often presents atypically with extrapulmonary (systemic) disease a common feature. Symptoms are usually constitutional and are not localized to one particular site, often affecting bone marrow, bone, urinary and gastrointestinal tracts, liver, regional lymph nodes, and the central nervous system. Alternatively, symptoms may relate more to the site of extrapulmonary involvement.

Major gastro-intestinal illnesses

• Esophagitis is an inflammation of the lining of the lower end of the esophagus (gullet or swallowing tube leading to the stomach). In HIV infected individuals, this is normally due to fungal ( candidiasis) or viral ( herpes simplex-1 or cytomegalovirus) infections. In rare cases, it could be due to mycobacteria.
• Unexplained chronic diarrhea in HIV infection is due to many possible causes, including common bacterial ( Salmonella, Shigella, Listeria, Campylobacter, or Escherichia coli) and parasitic infections, and uncommon opportunistic infections such as cryptosporidiosis, microsporidiosis, Mycobacterium avium complex (MAC) and cytomegalovirus (CMV) colitis. In some cases, diarrhea may be a side effect of several drugs used to treat HIV, or it may simply accompany HIV infection, particularly during primary HIV infection. It may also be a side effect of antibiotics used to treat bacterial causes of diarrhea (common for Clostridium difficile). In the later stages of HIV infection, diarrhea is thought to be a reflection of changes in the way the intestinal tract absorbs nutrients, and may be an important component of HIV-related wasting.

Major neurological illnesses

• Toxoplasmosis is a disease caused by the single-celled parasite called Toxoplasma gondii; it usually infects the brain causing toxoplasma encephalitis but it can infect and cause disease in the eyes and lungs.
• Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease, in which the gradual destruction of the myelin sheath covering the axons of nerve cells impairs the transmission of nerve impulses. It is caused by a virus called JC virus which occurs in 70% of the population in latent form, causing disease only when the immune system has been severely weakened, as is the case for AIDS patients. It progresses rapidly, usually causing death within months of diagnosis.
• AIDS dementia complex (ADC) is a metabolic encephalopathy induced by HIV infection and fuelled by immune activation of HIV infected brain macrophages and microglia which secrete neurotoxins of both host and viral origin. Specific neurological impairments are manifested by cognitive, behavioural, and motor abnormalities that occur after years of HIV infection and is associated with low CD4⁺ T cell levels and high plasma viral loads. Prevalence is 10-20% in Western countries but only 1-2% of HIV infections in India. This difference is possibly due to the HIV subtype in India.
• Cryptococcal meningitis is an infection of the meninx (the membrane covering the brain and spinal cord) by the fungus Cryptococcus neoformans. It can cause fevers, headache, fatigue, nausea, and vomiting. Patients may also develop seizures and confusion; left untreated, it can be lethal.

Major HIV-associated malignancies

Patients with HIV infection have substantially increased incidence of several malignant cancers. This is primarily due to co-infection with an oncogenic DNA virus, especially Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), and human papillomavirus (HPV). The following confer a diagnosis of AIDS when they occur in an HIV-infected person.

• Kaposi's sarcoma (KS) is the most common tumor in HIV-infected patients. The appearance of this tumor in young homosexual men in 1981 was one of the first signals of the AIDS epidemic. Caused by a gammaherpes virus called Kaposi's sarcoma-associated herpes virus (KSHV), it often appears as purplish nodules on the skin, but can affect other organs, especially the mouth, gastrointestinal tract, and lungs.
• High-grade B cell lymphomas such as Burkitt's lymphoma, Burkitt's-like lymphoma, diffuse large B-cell lymphoma (DLBCL), and primary central nervous system lymphoma present more often in HIV-infected patients. These particular cancers often foreshadow a poor prognosis. In some cases these lymphomas are AIDS-defining. Epstein-Barr virus (EBV) or KSHV cause many of these lymphomas.
• Cervical cancer in HIV-infected women is considered AIDS-defining. It is caused by human papillomavirus (HPV).

In addition to the AIDS-defining tumors listed above, HIV-infected patients are at increased risk of certain other tumors, such as Hodgkin's disease and anal and rectal carcinomas. However, the incidence of many common tumors, such as breast cancer or colon cancer, does not increase in HIV-infected patients. In areas where HAART is extensively used to treat AIDS, the incidence of many AIDS-related malignancies has decreased, but at the same time malignant cancers overall have become the most common cause of death of HIV-infected patients.

Other opportunistic infections

AIDS patients often develop opportunistic infections that present with non-specific symptoms, especially low-grade fevers and weight loss. These include infection with Mycobacterium avium-intracellulare and cytomegalovirus (CMV). CMV can cause colitis, as described above, and CMV retinitis can cause blindness. Penicilliosis due to Penicillium marneffei is now the third most common opportunistic infection (after extrapulmonary tuberculosis and cryptococcosis) in HIV-positive individuals within the endemic area of Southeast Asia.

Treatment

There is currently no vaccine or cure for HIV or AIDS. The only known methods of prevention are based on avoiding exposure to the virus or, failing that, an antiretroviral treatment directly after a highly significant exposure, called post-exposure prophylaxis (PEP). PEP has a very demanding four week schedule of dosage. It also has very unpleasant side effects including diarrhea, malaise, nausea and fatigue.

Current treatment for HIV infection consists of highly active antiretroviral therapy, or HAART. This has been highly beneficial to many HIV-infected individuals since its introduction in 1996 when the protease inhibitor-based HAART initially became available. Current optimal HAART options consist of combinations (or "cocktails") consisting of at least three drugs belonging to at least two types, or "classes," of anti-retroviral agents. Typical regimens consist of two nucleoside analogue reverse transcriptase inhibitors (NARTIs or NRTIs) plus either a protease inhibitor or a non-nucleoside reverse transcriptase inhibitor (NNRTI). Because HIV disease progression in children is more rapid than in adults, and laboratory parameters are less predictive of risk for disease progression, particularly for young infants, treatment recommendations are more aggressive for children than for adults. In developed countries where HAART is available, doctors assess the viral load, rapidity in CD4 decline, and patient readiness while deciding when to recommend initiating treatment.

HAART allows the stabilisation of the patient’s symptoms and viremia, but it neither cures the patient of HIV, nor alleviates the symptoms, and high levels of HIV-1, often HAART resistant, return once treatment is stopped. Moreover, it would take more than the lifetime of an individual to be cleared of HIV infection using HAART. Despite this, many HIV-infected individuals have experienced remarkable improvements in their general health and quality of life, which has led to the plummeting of HIV-associated morbidity and mortality. In the absence of HAART, progression from HIV infection to AIDS occurs at a median of between nine to ten years and the median survival time after developing AIDS is only 9.2 months. Still, for some patients - and in many clinical cohorts this may be more than fifty percent of patients - HAART achieves far less than optimal results. This is due to a variety of reasons such as medication intolerance/side effects, prior ineffective antiretroviral therapy and infection with a drug-resistant strain of HIV. However, non-adherence and non-persistence with antiretroviral therapy is the major reason most individuals fail to get any benefit from and develop resistance to HAART. The reasons for non-adherence and non-persistence with HAART are varied and overlapping. Major psychosocial issues, such as poor access to medical care, inadequate social supports, psychiatric disease and drug abuse contribute to non-adherence. The complexity of these HAART regimens, whether due to pill number, dosing frequency, meal restrictions or other issues along with side effects that create intentional non-adherence also has a weighty impact. The side effects include lipodystrophy, dyslipidaemia, insulin resistance, an increase in cardiovascular risks and birth defects.

Anti-retroviral drugs are expensive, and the majority of the world's infected individuals do not have access to medications and treatments for HIV and AIDS. Research to improve current treatments includes decreasing side effects of current drugs, further simplifying drug regimens to improve adherence, and determining the best sequence of regimens to manage drug resistance. Only a vaccine is postulated to be able to halt the pandemic. This is because a vaccine would possibly cost less, thus being affordable for developing countries, and would not require daily treatments. However, after over 20 years of research, HIV-1 remains a difficult target for a vaccine.

A number of studies have shown that measures to prevent opportunistic infections can be beneficial when treating patients with HIV infection or AIDS. Vaccination against hepatitis A and B is advised for patients who are not infected with these viruses and are at risk of becoming infected. In addition, AIDS patients should receive vaccination against Streptococcus pneumoniae and should receive yearly vaccination against influenza virus. Patients with substantial immunosuppression are also advised to receive prophylactic therapy for Pneumocystis jiroveci pneumonia (PCP), and many patients may benefit from prophylactic therapy for toxoplasmosis and Cryptococcus meningitis.

Various forms of alternative medicine have been used to try to treat symptoms or to try to affect the course of the disease itself, although none is a substitute for conventional treatment. In the first decade of the epidemic when no useful conventional treatment was available, a large number of people with AIDS experimented with alternative therapies. The definition of "alternative therapies" in AIDS has changed since that time. Then, the phrase often referred to community-driven treatments, untested by government or pharmaceutical company research, that some hoped would directly suppress the virus or stimulate immunity against it. These kinds of approaches have become less common over time as the benefits of AIDS drugs have become more apparent. Examples of alternative medicine that people hoped would improve their symptoms or their quality of life include massage, herbal and flower remedies and acupuncture; when used with conventional treatment, many now refer to these as "complementary" approaches. None of these treatments has been proven in controlled trials to have any effect in treating HIV or AIDS directly. However, some may improve feelings of well-being in people who believe in their value. Additionally, people with AIDS, like people with other illnesses such as cancer, sometimes use marijuana to treat pain, combat nausea and stimulate appetite.

Epidemiology

UNAIDS and the WHO estimate that AIDS has killed more than 25 million people since it was first recognized in 1981, making it one of the most destructive epidemics in recorded history. Despite recent, improved access to antiretroviral treatment and care in many regions of the world, the AIDS epidemic claimed an estimated 2.8 million (between 2.4 and 3.3 million) lives in 2005 of which more than half a million (570,000) were children.

Globally, between 33.4 and 46 million people currently live with HIV. In 2005, between 3.4 and 6.2 million people were newly infected and between 2.4 and 3.3 million people with AIDS died, an increase from 2003 and the highest number since 1981.

Sub-Saharan Africa remains by far the worst affected region, with an estimated 21.6 to 27.4 million people currently living with HIV. Two million [1.5–3.0 million] of them are children younger than 15 years of age. More than 64% of all people living with HIV are in sub-Saharan Africa, as are more than three quarters (76%) of all women living with HIV. In 2005, there were 12.0 million [10.6–13.6 million] AIDS orphans living in sub-Saharan Africa 2005. South & South East Asia are second worst affected with 15%. AIDS accounts for the deaths of 500,000 children in this region. Two-thirds of HIV/AIDS infections in Asia occur in India, with an estimated 5.7 million infections (estimated 3.4 - 9.4 million) (0.9% of population), surpassing South Africa's estimated 5.5 million (4.9-6.1 million) (11.9% of population) infections, making it the country with the highest number of HIV infections in the world. In the 35 African nations with the highest prevalence, average life expectancy is 48.3 years— 6.5 years less than it would be without the disease.

The latest evaluation report of the World Bank's Operations Evaluation Department assesses the effectiveness of the World Bank's country-level HIV/AIDS assistance, defined as policy dialogue, analytic work, and lending, with the explicit objective of reducing the scope or impact of the AIDS epidemic. This is the first comprehensive evaluation of the World Bank's HIV/AIDS support to countries, from the beginning of the epidemic through mid-2004. Because the Bank's assistance is for implementation of government programs by government, it provides important insights on how national AIDS programs can be made more effective.

The development of HAART as effective therapy for HIV infection and AIDS has substantially reduced the death rate from this disease in those areas where it is widely available. This has created the misperception that the disease has gone away. In fact, as the life expectancy of persons with AIDS has increased in countries where HAART is widely used, the number of persons living with AIDS has increased substantially. In the United States, the number of persons with AIDS increased from about 35,000 in 1988 to over 220,000 in 1996.

In Africa, the number of MTCT and the prevalence of AIDS is beginning to reverse decades of steady progress in child survival. Countries such as Uganda are attempting to curb the MTCT epidemic by offering VCT (voluntary counseling and testing), PMTCT (prevention of mother-to-child transmission) and ANC (ante-natal care) services, which include the distribution of antiretroviral therapy.

Economic impact

HIV and AIDS retard economic growth by destroying human capital. UNAIDS has predicted outcomes for sub-Saharan Africa to the year 2025. These range from a plateau and eventual decline in deaths beginning around 2012 to a catastrophic continual growth in the death rate with potentially 90 million cases of infection.

Without proper nutrition, health care and medicine that is available in developed countries, large numbers of people in these countries are falling victim to AIDS. They will not only be unable to work, but will also require significant medical care. The forecast is that this will likely cause a collapse of economies and societies in the region. In some heavily infected areas, the epidemic has left behind many orphans cared for by elderly grandparents.

The increased mortality in this region will result in a smaller skilled population and labor force. This smaller labor force will be predominantly young people, with reduced knowledge and work experience leading to reduced productivity. An increase in workers’ time off to look after sick family members or for sick leave will also lower productivity. Increased mortality will also weaken the mechanisms that generate human capital and investment in people, through loss of income and the death of parents. By killing off mainly young adults, AIDS seriously weakens the taxable population, reducing the resources available for public expenditures such as education and health services not related to AIDS resulting in increasing pressure for the state's finances and slower growth of the economy. This results in a slower growth of the tax base, an effect that will be reinforced if there are growing expenditures on treating the sick, training (to replace sick workers), sick pay and caring for AIDS orphans. This is especially true if the sharp increase in adult mortality shifts the responsibility and blame from the family to the government in caring for these orphans.

On the level of the household, AIDS results in both the loss of income and increased spending on healthcare by the household. The income effects of this lead to spending reduction as well as a substitution effect away from education and towards healthcare and funeral spending. A study in Côte d'Ivoire showed that households with an HIV/AIDS patient spent twice as much on medical expenses as other households.

UNAIDS, WHO and the United Nations Development Programme have documented a correlation between the decreasing life expectancies and the lowering of gross national product in many African countries with prevalence rates of 10% or more. Indeed, since 1992 predictions that AIDS would slow economic growth in these countries have been published. The degree of impact depended on assumptions about the extent to which illness would be funded by savings and who would be infected. Conclusions reached from models of the growth trajectories of 30 sub-Saharan economies over the period 1990–2025 were that the economic growth rates of these countries would be between 0.56 and 1.47% lower. The impact on gross domestic product (GDP) per capita was less conclusive. However, in 2000, the rate of growth of Africa's per capita GDP was in fact reduced by 0.7% per year from 1990–1997 with a further 0.3% per year lower in countries also affected by malaria. The forecast now is that the growth of GDP for these countries will undergo a further reduction of between 0.5 and 2.6% per annum. However, these estimates may be an underestimate, as they do not look at the effects on output per capita.

Many governments in sub-Saharan Africa denied that there was a problem for years, and are only now starting to work towards solutions. Underfunding is a problem in all areas of HIV prevention when compared to even conservative estimates of the problems.

The launching of the world's first official HIV/AIDS Toolkit in Zimbabwe on October 3, 2006 is a product of collaborative work between the International Federation of Red Cross and Red Crescent Societies, World Health Organization and the Southern Africa HIV/AIDS Information Dissemination Service. It is for the strengthening of people living with HIV/AIDS and nurses by minimal external support. The package, which is in form of eight modules focusing on basic facts about HIV and AIDS, was pre-tested in Zimbabwe in March 2006 to determine its adaptability. It disposes, among other things, categorized guidelines on clinical management, education and counseling of AIDS victims at community level.

The Copenhagen Consensus is a project that seeks to establish priorities for advancing global welfare using methodologies based on the theory of welfare economics. The participants are all economists, with the focus of the project being a rational prioritization based on economic analysis. The project is based on the contention that, in spite of the billions of dollars spent on global challenges by the United Nations, the governments of wealthy nations, foundations, charities, and non-governmental organizations, the money spent on problems such as malnutrition and climate change is not sufficient to meet many internationally-agreed targets. The highest priority was assigned to implementing new measures to prevent the spread of HIV and AIDS. The economists estimated that an investment of $27 billion could avert nearly 30 million new infections by 2010.

Stigma

AIDS stigma exists around the world in a variety of ways, including ostracism, rejection, discrimination and avoidance of HIV infected people; compulsory HIV testing without prior consent or protection of confidentiality; violence against HIV infected individuals or people who are perceived to be infected with HIV; and the quarantine of HIV infected individuals.

AIDS stigma has been further divided into the following three categories:

1. Instrumental AIDS stigma—a reflection of the fear and apprehension that are likely to be associated with any deadly and transmissible illness.
2. Symbolic AIDS stigma—the use of HIV/AIDS to express attitudes toward the social groups or lifestyles perceived to be associated with the disease.
3. Courtesy AIDS stigma—stigmatization of people connected to the issue of HIV/AIDS or HIV- positive people.

Often, AIDS stigma is expressed in conjunction with one or more other stigmas, particularly those associated with homosexuality, bisexuality, and intravenous drug use.

In many developed countries, there is an association between AIDS and homosexuality or bisexuality, and this association is correlated with higher levels of sexual prejudice such as anti-homosexual attitudes. There is also a perceived association between all male-male sexual behaviour and AIDS, even sex between two uninfected men.

For more details on this topic, see Stigma and HIV-AIDS, A review of the literature

Origin of HIV

AIDS was first reported June 5, 1981, when the U.S. Centers for Disease Control and Prevention recorded a cluster of Pneumocystis carinii pneumonia (now classified as Pneumocystis jiroveci pneumonia) in five homosexual men in Los Angeles. Originally dubbed GRID, or Gay-Related Immune Deficiency, health authorities soon realized that nearly half of the people identified with the syndrome were not homosexual men. In 1982, the CDC introduced the term AIDS to describe the newly recognized syndrome.

Three of the earliest known instances of HIV infection are as follows:

1. A plasma sample taken in 1959 from an adult male living in what is now the Democratic Republic of the Congo.
2. HIV found in tissue samples from a 15 year old African-American teenager who died in St. Louis in 1969.
3. HIV found in tissue samples from a Norwegian sailor who died around 1976.

Two species of HIV infect humans: HIV-1 and HIV-2. HIV-1 is more virulent and more easily transmitted. HIV-1 is the source of the majority of HIV infections throughout the world, while HIV-2 is not as easily transmitted and is largely confined to West Africa. Both HIV-1 and HIV-2 are of primate origin. The origin of HIV-1 is the Central Common Chimpanzee (Pan troglodytes troglodytes) found in southern Cameroon. It is established that HIV-2 originated from the Sooty Mangabey (Cercocebus atys), an Old World monkey of Guinea Bissau, Gabon, and Cameroon.

Most experts believe that HIV probably transferred to humans as a result of direct contact with primates, for instance during hunting or butchery. A more controversial theory known as the OPV AIDS hypothesis suggests that the AIDS epidemic was inadvertently started in the late 1950s in the Belgian Congo by Hilary Koprowski's research into a polio vaccine. According to scientific consensus, this scenario is not supported by the available evidence.

Alternative hypotheses

A small minority of scientists and activists question the connection between HIV and AIDS, the existence of HIV itself, or the validity of current testing and treatment methods. These claims are considered baseless by the vast majority of the scientific community. The medical community argues that so-called "AIDS dissidents" selectively ignore evidence in favour of HIV's role in AIDS and irresponsibly pose a threat to public health by discouraging HIV testing and proven treatments.

AIDS dissidents assert that the current mainstream approach to AIDS, based on HIV causation, has resulted in inaccurate diagnoses, psychological terror, toxic treatments, and a squandering of public funds. Dissident views have been widely rejected, and are considered pseudoscience by the mainstream scientific community.

Common misconceptions

A number of misconceptions have arisen surrounding HIV/AIDS. Three of the most common are that AIDS can spread through casual contact, sexual intercourse with a virgin will cure AIDS, and HIV can infect only homosexual men and drug users.

When scientists first recognized the syndrome in 1981 initially they termed it Gay Related Immune Deficiency Syndrome, a possible source for the misconception holding that AIDS infects only homosexual men; scientists soon renamed the disease in recognition of transmission other than by male-male intercourse.

HIV appears to have entered the United States around the late 1960s and seems to have then been unknowingly spread by people throughout the U.S. and Europe. In a survey on AIDS conducted in 1983 in Belgium, Denmark, Finland, France, Germany, Italy, the Netherlands, Norway, Sweden, Switzerland, and the United Kingdom a majority of those infected with HIV were male homosexuals (58% of all cases).