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AIDS is an acronym for Acquired Immunodeficiency Syndrome or Acquired Immune Deficiency Syndrome and is defined as a collection of symptoms and infections resulting from the depletion of the immune system caused by infection with the human immunodeficiency virus, commonly called HIV (Marx et al., 1982). Although treatments for both AIDS and HIV exist to slow the virus' progression in a human patient, there is no known cure. The rate of clinical disease progression varies widely between individuals and has been shown to be affected by many factors such as host susceptibility (Clerici et al., 1996; Morgan et al., 2002a; Tang et al., 2003), health care and co-infections (Morgan et al., 2002b; Lawn et al., 2004), and peculiarities of the viral strain (Campbell et al., 2004; Campbell et al., 2005; Senkaali et al., 2005). AIDS is thought to have originated in sub-Saharan Africa (Gao et al., 1999) during the twentieth century and is now a global epidemic. 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. In 2005 alone, AIDS claimed an estimated 3.1 million (between 2.8 and 3.6 million) of which more than half a million (570,000) were children (UNAIDS, 2005).

In countries where there is access to antiretroviral treatment, both mortality and morbidity of HIV infection have been reduced (Palella et al., 1998). However, side-effects of these antiretrovirals have also caused problem such as lipodystrophy, dyslipidaemia, insulin resistance and an increase in cardiovascular risks (Montessori et al., 2004), or viral escape and resistance linked to non-observance of the antiretroviral regimen (Becker et al., 2002).

Contents 1 Symptomology 1.1 AIDS and HIV case definitions 1.1.1 WHO Disease Staging System for HIV Infection and Disease 1.1.2 CDC Classification System for HIV Infection 1.2 Clinical symptoms of AIDS 1.2.1 The major pulmonary illnesses 1.2.1.1 Pneumocystis jiroveci pneumonia 1.2.1.2 Tuberculosis 1.2.2 The major gastro-intestinal illnesses 1.2.2.1 Esophagitis 1.2.2.2 Unexplained chronic diarrhea 1.2.3 The major neurological illnesses 1.2.3.1 Toxoplasmosis 1.2.3.2 Progressive multifocal leukoencephalopathy 1.2.3.3 HIV-associated dementia 2 Transmission 3 Prevention 3.1 Prevention of sexual transmission of HIV 3.1.1 Underlying science 3.1.2 Prevention strategies 3.1.3 Governmental programs 3.1.4 Circumcision 3.2 Prevention of blood or blood product route of HIV transmission 3.2.1 Underlying science 3.2.2 Prevention strategies 3.3 Mother to child transmission 3.3.1 Underlying science 3.3.2 Prevention strategies 4 Treatment 4.1 Alternative medicine 5 HIV test 6 Epidemiology 7 Origin of HIV/AIDS 8 Alternative theories 9 References 10 External links 11 AIDS News

Symptomology

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, parasites, and other organisms. Opportunistic infections are common in people with AIDS (Holmes et al., 2003). Nearly every organ system is affected. People with AIDS also have an increased risk to develop various cancers such as Kaposi sarcoma, cervical cancer and cancers of the immune system known as lymphomas. Common symptoms are fevers, sweats (particularly at night), swollen glands, chills, weakness, and weight loss (Guss, 1994a; 1994b). After the diagnosis of AIDS is made, the current average survival time with antiretroviral therapy is estimated to be between 4 to 5 years (Schneider et al., 2005). Without this therapy, progression to death normally occurs within a year (Morgan et al., 2002b). Most patients die from opportunistic infections or malignancies associated with the progressive failure of the immune system (Lawn et al., 2004).

AIDS and HIV case definitions

Since 1982, many different definitions have been developed for epidemiological surveillance such as the Bangui definition and the 1994 expanded World Health Organization AIDS case definition. However, these were never intended to be used for clinical staging of patients, for which they are neither sensitive nor specific. The World Health Organizations (WHO) staging system for HIV infection and disease, using clinical and laboratory data, can be used in developing countries and the Centers for Disease Control (CDC) Classification System can be used in developed nations.

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 (WHO, 1990). This was updated in September 2005. Most of these conditions are opportunistic infections that can be easily treated in healthy people.

• Stage I: HIV disease is asymptomatic and not categorized as AIDS
• Stage II: include 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 or
• Stage IV includes toxoplasmosis of the brain, candidiasis of the esophagus, trachea, bronchi or lungs and Kaposi's sarcoma; these diseases are used as indicators of AIDS.

For more details on this topic, see WHO Disease Staging System for HIV Infection and Disease.

CDC Classification System for HIV Infection

In the USA, the definition of AIDS is goverened by the Centers for Disease Control and Prevention (CDC). In 1993, the CDC expanded their definition of AIDS to include healthy HIV positive people with a CD4 positive T cell count of less than 200 per µl of blood. The majority of new AIDS cases in the United States are reported on the basis of a low T cell count in the presence of HIV infection (MMWR, 1992).

For more details on this topic, see CDC Classification System for HIV Infection.

Clinical symptoms of AIDS

The major pulmonary illnesses

Pneumocystis jiroveci pneumonia

Pneumocystis jiroveci pneumonia (originally known as Pneumocystis carinii pneumonia, often abbreviated PCP) is relatively rare in normal, immunocompetent people but common among HIV-infected individuals. Before the advent of effective treatment and diagnosis 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 (Feldman, 2005).

Tuberculosis

Among infections associated with HIV, tuberculosis (TB) is unique in that it may be transmitted to immunocompetent persons via the respiratory route, is easily treatable once identified, may occur in early-stage HIV disease, and is preventable with drug therapy. However, multi-drug 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 may present atypically and extrapulmonary TB is common infecting bone marrow, bone, urinary and gastrointestinal tracts, liver, regional lymph nodes, and the central nervous system (Decker and Lazarus, 2000).

The major gastro-intestinal illnesses

Esophagitis

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 could be due to fungus (candidiasis), virus (herpes simplex-1 or cytomegalovirus). In rare cases, it could be due to mycobacteria (Zaidi and Cervia, 2002).

Unexplained chronic diarrhea

In HIV infection, there are many possible causes of diarrhea, 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. Diarrhea may follow a course of antibiotics (common for Clostridium difficile). It may also be a side effect of several drugs used to treat HIV, or it may simply accompany HIV infection, particularly during primary HIV infection. 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 (Guerrant et al., 1990).

The major neurological illnesses

Toxoplasmosis

Toxoplasmosis is a disease caused by the single-celled parasite called Toxoplasma gondii. T. gondii usually infects the brain causing toxoplasma encephalitis. It can also infect and cause disease in the eyes and lungs (Luft and Chua, 2000).

Progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease, in which the myelin sheath covering the axons of nerve cells is gradually destroyed, impairing 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 severly weakened, as is the case for AIDS patients. It progresses rapidly, usually causing death within months of diagnosis (Sadler and Nelson, 1997).

HIV-associated dementia

HIV-1 associated dementia (HAD) is a metabolic encephalopathy induced by HIV infection and fueled by immune activation of brain macrophages and microglia (Gray et al., 2001). These cells are actively infected with HIV and secrete neurotoxins of both host and viral origin. Specific neurologic impairments are manifested by cognitive, behavioral, 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 between 15-30% in Western countries (Heaton et al., 1995; White et al., 1995) and has only been seen in 1-2% of India based infections (Satischandra et al., 2000; Wadia et al., 2001).

Transmission

Since the beginning of the epidemic, three main transmission routes of HIV have been identified:

• Sexual route. The majority of HIV infections have been, and still are, acquired through unprotected sexual relations. Sexual transmission occurs when there is contact between sexual secretions of one partner with the rectal, genital or mouth mucous membranes of another.

• Blood or blood product route. This transmission route is particularly important for intravenous drug users, hemophiliacs and recipients of blood transfusions and blood products. Health care workers (nurses, laboratory workers, doctors etc) are also concerned, although more rarely. Also concerned by this route are people who give and receive tattoos and piercings.

• Mother-to-child route. The transmission of the virus from the mother to the child can occur in utero during the last weeks of pregnancy and at childbirth. Breast feeding also presents a risk of infection for the baby. In the absence of treatment, the transmission rate between the mother and child was 20%. However, where treatment is available, combined with the availability of Cesarian section, this has been reduced to 1%.

HIV has been found in the saliva, tears and urine of infected individuals, but due to the low concentration of virus in these biological liquids, the risk is considered to be negligible.

Prevention

The diverse transmission routes of HIV are well-known and established. Also well-known is how to prevent transmission of HIV. However, recent epidemiological and behavioral studies in Europe and North America have suggested that a substantial minority of young people continue to engage in high-risk practices and that despite HIV/AIDS knowledge, young people underestimate their own risk of becoming infected with HIV (Dias et al., 2005). However, transmission of HIV between intravenous drug users has clearly decreased and HIV transmission by blood transfusion has become almost obsolete in this population.

Prevention of sexual transmission of HIV

Underlying science

• Unprotected receptive sexual acts are at more risk than unprotected insertive sexual acts, with the risk for transmitting HIV from an infected partner to an uninfected partner through unprotected insertive anal intercourse (UIAI) greater than the risk for transmission through receptive anal intercourse or oral sex. According to the French ministry for health, the probability of transmission per act varies from 0.03% to 0.07% for the case of receptive vaginal sex, from 0.02 to 0.05% in the case of insertive vaginal sex, from 0.01% to 0.185% in the case of insertive anal sex, and 0.5% to 3% in the case of receptive anal sex [1].

• Sexually-transmitted infections (STI) increase the risk of HIV transmission and infection because they cause the disruption of the normal epithelial barrier by genital ulceration and/or microulceration; and by accumulation of pools of HIV-susceptible or HIV-infected cells (lymphocytes and macrophages) in semen and vaginal secretions. Epidemiological studies from sub-Saharan Africa, Europe and North America have suggested that there is approximately, a four times greater risk of becoming HIV-infected in the presence of a genital ulcer such as caused by syphilis and/or chancroid; and a significant though lesser increased risk in the presence of STIs such as gonorrhoea, chlamydial infection and trichomoniasis which cause local accumulations of lymphocytes and macrophages (Laga et al., 1991).

• Transmission of HIV depends on the infectiousness of the index case and the susceptibility of the uninfected partner. Infectivity seems to vary during the course of illness and is not constant between individuals. An undetectable plasma viral load does not mean that you have a low viral load in the seminal liquid or genital secretions. Each 10 fold increment of seminal HIV RNA is associated with an 81% increased rate of HIV transmission (Tovanabutra et al., 2002).

• People who are infected with HIV can still be infected by other, more virulent strains.

• Oral sex is not without its risks as it has been established that HIV can be transmitted through both insertive and receptive oral sex (Rothenberg et al., 1998).

• Women are more susceptible to HIV-1 due to hormonal changes, vaginal microbial ecology and physiology, and a higher prevalence of sexually transmitted diseases (Sagar et al., 2004; Lavreys et al., 2004).

Prevention strategies

During a sexual act, only condoms, be they male or female, can reduce the chances of infection with HIV and other STIs and the chances of becoming pregnant. They must be used during all penetrative sexual intercourse with a partner who is HIV positive or whose status is unknown (Cayley, 2004). The effective use of condoms and screening of blood transfusion in North America, Western and Central Europe is credited with the low rates of AIDS in these regions. Adopting these effective prevention methods in other regions has proved controversial and difficult. Some claim this is in part because of the strong influence of the Roman Catholic Church, which opposes the use of condoms.

• The male latex condom is the single most efficient available technology to reduce the sexual transmission of HIV and other sexually transmitted infections. In order to be effective, they must be used correctly during each sexual act. Lubricants containing oil, such as petroleum jelly, or butter, must not be used as they weaken latex condoms and make them porous. If necessary, lubricants made from water are recommended. However, it is not recommended to use a lubricant for fellatio. Also, condoms have standards and expiration dates. It is essential to check the expiration date and if it conforms to European (EC 600) or American (D3492) standards before use.

• The female condom is an alternative to the male condom and is made from polyurethane, which allows it to be used in the presence of oil-based lubricants. They are larger than male condoms and have a stiffened ring-shaped opening, and are designed to be inserted into the vagina. The female condom also contains an inner ring which keeps the condom in place inside the vagina - inserting the female condom requires squeezing this ring.

With consistent and correct use of condoms, there is a very low risk of HIV infection. Studies on couples where one partner is infected show that with consistent condom use, HIV infection rates for the uninfected partner are below 1% per year [2].

Governmental programs

The U.S. government and U.S. health organizations both endorse the ABC Approach to lower the risk of acquiring AIDS during sex:

• Abstinence or delay of sexual activity, especially for youth,
• Being faithful, especially for those in committed relationships,
• Condom use, for those who engage in risky behavior.

This approach has been very successful in Uganda, where HIV prevalence has decreased from 15% to 5%. However, the ABC approach is far from all that Uganda has done, as "Uganda has pioneered approaches towards reducing stigma, bringing discussion of sexual behavior out into the open, involving HIV-infected people in public education, persuading individuals and couples to be tested and counseled, improving the status of women, involving religious organizations, enlisting traditional healers, and much more." (Edward Green, Harvard medical anthropologist). Also, it must be noted that there is no conclusive proof that abstinence-only programs have been successful in any country in the world in reducing HIV transmission. This is why condom use is heavily co-promoted. There is also considerable overlap with the CNN Approach. This is:

• Condom use, for those who engage in risky behavior.
• Needles, use clean ones
• Negotiating skills; negotiating safer sex with a partner and empowering women to make smart choices

The ABC approach has been criticized, because a faithful partner of an unfaithful partner is at risk of AIDS [3]. Many think that the combination of the CNN approach with the ABC approach will be the optimum prevention platform.

Circumcision

Current research is clarifying the relationship between male circumcision and HIV in differing social and cultural contexts. UNAIDS believes that it is premature to recommend male circumcision services as part of HIV prevention programmes [4].

Moreover, South African medical experts are concerned that the repeated use of unsterilised blades in the ritual circumcision of adolescent boys may be spreading HIV. [5]

Prevention of blood or blood product route of HIV transmission

Underlying science

• Sharing and reusing syringes contaminated with HIV-infected blood represents a major risk for infection with not only HIV but also hepatitis B and C. In the United States a third of all new HIV infections can be traced to needle sharing and almost 50% of long-term addicts have hepatitis C.

• The risk of being infected with HIV from a single prick with a needle that has been used on an HIV infected person though is thought to be about 1 in 150 (see table above). Post-exposure prophylaxis with anti-HIV drugs can further reduce that small risk [6].

• Universal precautions are frequently not followed in both sub-Saharan Africa and much of Asia because of both a shortage of supplies and inadequate training. The WHO estimates that approximately 2.5% of all HIV infections in sub-Saharan Africa are transmitted through unsafe healthcare injections. [7]. Because of this, the United Nations General Assembly, supported by universal medical opinion on the matter, has urged the nations of the world to implement universal precautions to prevent HIV transmission in health care settings [8].

Prevention strategies

• In those countries where improved donor selection and antibody tests have been introduced, the risk of transmitting HIV infection to blood transfusion recipients has been effectively eliminated. According to the WHO, the overwhelming majority of the world's population does not have access to safe blood and "between 5% and 10% of HIV infections worldwide are transmitted through the transfusion of infected blood and blood products." [9]

• Medical workers who follow universal precautions or body substance isolation such as wearing latex gloves when giving injections and washing the hands frequently can help prevent infection of HIV.

• All AIDS-prevention organizations advise drug-users not to share needles and other material required to prepare and take drugs (including syringes, cotton balls, the spoons, water for diluting the drug, straws, crack pipes etc). It is important that people use new or properly sterilized needles for each injection. Information on cleaning needles using bleach is available from health care and addiction professionals and from needle exchanges. In the United States and other western countries, clean needles are available free in some cities, at needle exchanges or safe injection sites.

Mother to child transmission

Underlying science

• There is a 15–30% risk of transmission of HIV from mother to child during pregnancy, labour and delivery (Orendi et al., 1998). In developed countries the risk can of transmission of HIV from mother to child can be as low as 0-5%. A number of factors influence the risk of infection, particularly the viral load of the mother at birth (the higher the load, the higher the risk). Breastfeeding increases the risk of transmission by 10–15%. This risk depends on clinical factors and may vary according to the pattern and duration of breastfeeding.

Prevention strategies

• Studies have shown that antiretroviral drugs, cesarean delivery and formula feeding reduce the chance of transmission of HIV from mother to child (Sperling et al., 1996).

• When replacement feeding is acceptable, feasible, affordable, sustainable and safe, HIV-infected mothers are recommended to avoid breast feeding their infant. Otherwise, exclusive breastfeeding is recommended during the first months of life and should be discontinued as soon as possible. [10]

Treatment

There is currently no cure or vaccine for HIV or AIDS. Infection with HIV leads to AIDS and ultimately death. However, in western countries, most patients survive many years following diagnosis because of the availability of the highly active antiretroviral therapy HAART (Schneider et al., 2005). 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 (Morgan et al., 2002b). HAART dramatically increases the time from diagnosis to death and research continues in drug treatments and vaccine development.

Current optimal HAART options consist of combinations ("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 (NRTIs) plus either a protease inhibitor or a non nucleoside reverse transcriptase inhibitor (NNRTI). This treatment is frequently referred to as HAART (highly-active anti-retroviral therapy). [11] Anti-retroviral treatments, along with medications intended to prevent AIDS-related opportunistic infections, have played a part in delaying complications associated with AIDS, reducing the symptoms of HIV infection, and extending patients' life spans. Over the past decade the success of these treatments in prolonging and improving the quality of life for people with AIDS has improved dramatically. [12], [13].

However, treatment guidelines are changing constantly. The current guidelines for antiretroviral therapy from the World Health Organization reflect the 2003 changes to the guidelines and recommend that in resource-limited settings (i.e., developing nations), HIV-infected adults and adolescents should start ARV therapy when HIV-infection has been confirmed and one of the following conditions is present:

• Clinically advanced HIV disease:
• WHO Stage IV HIV disease, irrespective of the CD4 cell count;
• WHO Stage III disease with consideration of using CD4 cell counts <350/µl to assist decision-making.
• WHO Stage I or II HIV disease with CD4 cell counts <200/µl

The U.S. Department of Health and Human Services, the federal agency responsible for overseeing HIV/AIDS healthcare policies in the United States, stated October 6, 2005that:

• All patients with history of an AIDS-defining illness or severe symptoms of HIV infection regardless of CD4+ T cell count receive ART.
• Antiretroviral therapy is also recommended for asymptomatic patients with <200 CD4+ T cells/µl
• Asymptomatic patients with CD4+ T cell counts of 201–350 cells/µl should be offered treatment.
• For asymptomatic patients with CD4+ T cell of >350 cells/µl and plasma HIV RNA >100,000 copies/ml most experienced clinicians defer therapy but some clinicians may consider initiating treatment.
• Therapy should be deferred for patients with CD4+ T cell counts of >350 cells/µl and plasma HIV RNA <100,000 copies/mL.

The preferred initial regimens are either:

• efavirenz + lamivudine or emtricitabine + zidovudine or tenofovir; or
• lopinavir boosted with ritonavir + zidovudine + lamivudine or emtricitabine.

The DHHS also recommends that doctors should assess the viral load, rapidity in CD4 decline, and patient readiness while deciding when to begin treatment. [14]

There are several concerns about antiretroviral regimens. The drugs can have serious side effects (Saitoh et al., 2005). Regimens can be complicated, requiring patients to take several pills at various times during the day. If patients miss doses, drug resistance can develop (Dybul et al., 2002) Also, anti-retroviral drugs are costly, 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, simplifying drug regimens to improve adherence, and determining the best sequence of regimens to manage drug resistance.

For a more detailed treatment of this topic, see the subarticles HIV vaccine and Antiretroviral drug.

Alternative medicine

Ever since AIDS entered the public consciousness, various forms of alternative medicine have been used to try to treat its symptoms. 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 (massage, herbal and flower remedies and acupuncture). However, none of these have been proven to have any positive effect in treating HIV. Interest in these therapies has declined over the past decade as conventional treatments have improved. People with AIDS, like people with other illnesses such as cancer, also sometimes use marijuana to treat pain, combat nausea and stimulate appetite.

HIV test

Nearly half of those infected with HIV don't know that they are infected until they are diagnosed with AIDS. HIV test kits are used to screen donor blood and blood products, and to diagnose, treat and monitor individuals with HIV. HIV tests detect HIV antibodies, HIV antigens or HIV RNA in serum, plasma, oral fluid, dried blood spot or urine of patients.

For more details on this topic, see HIV test.

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 3.1 million (between 2.8 and 3.6 million) lives in 2005 of which more than half a million (570,000) were children (UNAIDS, 2005).

Globally, between 36.7 and 45.3 million people are currently living with HIV (UNAIDS, 2005). In 2005, between 4.3 and 6.6 million people were newly infected and between 2.8 and 3.6 million people with AIDS died, an increase from 2004 and the highest number since 1981.

Sub-Saharan Africa remains by far the worst-affected region, with an estimated 23.8 to 28.9 million people currently living with HIV. More than 60% of all people living with HIV are in sub-Saharan Africa, as are more than three quarters (76%) of all women living with HIV. [15] South & South East Asia are second most affected with 15%. AIDS accounts for the deaths of 500,000 children.

The latest evaluation report of the World Bank's Operations Evaluation Department assesses the development 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.

For more details on this topic, see AIDS pandemic.

Origin of HIV/AIDS

The official date for the beginning of the AIDS epidemic is marked as June 18, 1981, when the U.S. Center for Disease Control and Prevention reported a cluster of Pneumocystis carinii pneumonia (now classified as Pneumocystis jiroveci pneumonia) in five gay men in Los Angeles in the early 1980s. [16] Originally dubbed GRID, or Gay-Related Immune Deficiency, health authorities soon realized that nearly half of the people identified with the syndrome were not gay. 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 Congo (Zhu et al., 1998).
2. HIV found in tissue samples from an 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 less easily transmitted and is largely confined to West Africa. (Reeves and Doms, 2002). Both HIV-1 and HIV-2 are of primate origin. The origin of HIV-1 is the Central Common Chimpanzee (Pan troglodytes troglodytes). The origin of HIV-2 has been established to be the Sooty Mangabey, an Old World monkey of Guinea Bissau, Gabon, and Cameroon.

For more details on this topic, see AIDS origin.

Alternative theories

A minority of scientists and activists question the connection between HIV and AIDS, or the existence of HIV, or the validity of current testing methods. These claims are met with resistance by, and often evoke frustration and hostility from, most of the scientific community, who accuse the dissidents of ignoring evidence in favor of HIV's role in AIDS, and irresponsibly posing a dangerous threat to public health by their continued activities. 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. The debate and controversy regarding this issue from the early 1980s to the present has provoked heated emotions and passions from both sides.

For more details on this topic, see AIDS reappraisal.

HIV/AIDS

HIV | AIDS

WHO Disease Staging System for HIV Infection and Disease | CDC Classification System for HIV Infection

HIV structure and genome | HIV Disease Progression Rates

HIV test | Antiretroviral drug | HIV vaccine

AIDS origin | AIDS pandemic | List of countries by HIV/AIDS adult prevalence rate

AIDS in Sub-Saharan Africa| | AIDS in the United States

Treatment Action Campaign | International AIDS Conferences | International AIDS Society| UNAIDS

World AIDS Day | List of AIDS-related topics | Timeline of AIDS

Common misconceptions about HIV and AIDS| OPV AIDS hypothesis

Reappraisal of HIV-AIDS Hypothesis | Duesberg hypothesis

NAMES Project AIDS Memorial Quilt | List of HIV-positive individuals

People With AIDS Self-Empowerment Movement | AIDS Museum | HIV-positive fictional characters

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Other references used in developing this article can be found at AIDS/references.

External links

• International AIDS Society - the world's leading independent association of HIV/AIDS professionals
• World AIDS Day World AIDS Day 1 December - Show your support
• AIDS Assistance Evaluating the World Bank's Assistance for Fighting the HIV/AIDS Epidemic
• AIDS.ORG AIDS.ORG: Educating - Raising HIV Awareness - Building Community
• AIDSinfo 2002 The Glossary of HIV/AIDS-Related Terms 4th Edition
• AIDSmeds.com 2005 AIDSmeds.com: Comprehensive lessons on HIV/AIDS and their treatments
• Center for Disease Control (2005). Divisions of HIV/AIDS Prevention
• FightAIDS@Home the distributed computing project against AIDS
• Health Action AIDS 2003 HIV Transmission in the Medical Setting
• NIAID/NIH 2003 Basic Information About AIDS and HIV
• NIAID/NIH 2003 Evidence That HIV causes AIDS
• NIAID/NIH 2004 How HIV Causes AIDS
• The Body 2005 The Body: The Complete HIV/AIDS Resource
• Origin of Aids Video Watch Free online : Origin of Aids Video
• UNAIDS 2005 The Joint United Nations Programme on HIV/AIDS
• Journal Watch 2005 AIDS Clinical Care
• UNAIDS Scenarios to 2025 Document regarding three scenarios for HIV/AIDS in Africa for the year 2025 (Large PDF file)

AIDS News

• Nov 2005 - Progress in HIV vaccine research -- Recorded interview with Prof. Robert Gallo (HIV discoverer)

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