HIV/AIDS

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The Red Ribbon symbol is used internationally to represent the fight against AIDS.

AIDS (Acquired Immunodeficiency Syndrome or Acquired Immune Deficiency Syndrome, rarely written Aids) is caused by the human immunodeficiency virus HIV, a lentivirus [1]. By leading to the destruction and/or functional impairment of cells of the immune system, notably CD4+ T cells, HIV progressively destroys the body's ability to fight infections and certain cancers. [2]

A person with antibodies to HIV, who has a CD4+ T cell count below 200/mm³ or an AIDS defining clinical condition, is diagnosed with AIDS. [3] Although treatments for AIDS exist, there is no cure.

HIV infection is acquired through penetrative (anal or vaginal) and oral sex; blood transfusion; the sharing of contaminated needles in health care settings and through drug injection; and, between mother and infant, during pregnancy, childbirth and breastfeeding. [4].

AIDS is thought to have originated in sub-Saharan Africa during the twentieth century and is now a global epidemic. The World Health Organization estimated that, worldwide, between 2.8 and 3.5 million people with AIDS died in 2004. [5]

Global epidemic

UNAIDS and the World Health Organization (WHO) estimated that between 36 and 44 million people around the world were living with HIV in December 2004 [6]. It was estimated that during 2004, between 4.3 and 6.4 million people were newly infected with HIV and between 2.8 and 3.5 million people with AIDS died. Sub-Saharan Africa remains by far the worst-affected region, with 23.4 million to 28.4 million people living with HIV at the end of 2004. Just under two thirds (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. [7] South & South East Asia are second most affected with 15%. AIDS accounts for the deaths of 500,000 children.

World region	Estimated adult prevalence of HIV infection (ages 15–49)	Estimated adult and child deaths during 2004
Sub-Saharan Africa	6.9% to 8.3%	2.1 to 2.6 million
Caribbean	1.5% to 4.1%	24,000 to 61,000
Asia	0.3% to 0.6%	350,000 to 810,000
Eastern Europe and Central Asia	0.5% to 1.2%	39,000 to 87,000
Latin America	0.5% to 0.8%	73,000 to 120,000
Oceania	0.1% to 0.3%	fewer than 1,700
Middle East and North Africa	0.1% to 0.7%	12,000 to 72,000
North America, Western and Central Europe	0.3% to 0.6%	15,000 to 32,000

Source: UNAIDS and the WHO 2004 estimates. The ranges define the boundaries within which the actual numbers lie, based on the best available information. [8]

Main article: AIDS pandemic

Prevention

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CDC 2005

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. The Vatican opposes the use of condoms [9] and many countries do not screen blood transfusions for HIV antibodies.

Safer sex

Correct and consistent use of a condom significantly reduces the risk of acquiring AIDS and is advocated by health experts around the world.

Health organizations 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.

The ABC approach has been criticized, because a faithful husband or wife of an unfaithful partner is at risk of AIDS. [10].

HIV blood screening

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." [11]

Medical procedures

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. 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. [12]

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. [13]. 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 [14].

Intravenous drug use

HIV can be transmitted by the sharing of needles by users of intravenous drugs. Cumulative data from 1981 to 2001 has shown that 31% of people with AIDS in the United States are injection drug users [15]. All AIDS-prevention organisations advise drug-users not to share needles and to use a new or properly sterilized needle 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

About one in four babies born to HIV infected mothers are infected with HIV. Studies have shown that antiretroviral drugs, cesarean delivery and formula feeding reduce the chance of transmission of HIV from mother to child. [16]

When replacement feeding is acceptable, feasible, affordable, sustainable and safe, avoiding breast feeding by HIV infected mothers is recommended. Otherwise, exclusive breastfeeding is recommended during the first months of life and should be discontinued as soon as possible. [17]

Transmission and infection

Scanning electron micrograph of HIV-1 budding from cultured lymphocyte.

Patterns of HIV transmission vary in different parts of the world. In sub-Saharan Africa, which accounts for an estimated 60% of new HIV infections worldwide, controversy rages over the respective contribution of medical procedures, heterosexual sex and the bush meat trade. In the United States, sex between men (35%) and needle sharing by intravenous drug users (15%) remain prominent sources of new HIV infections. [18] In January 2005, Anthony S. Fauci, M.D., director of NIAID said, "Individual risk of acquiring HIV and experiencing rapid disease progression is not uniform within populations". NIH press release Some epidemiological models suggest that over half of HIV transmission occurs in the weeks following primary HIV infection before antibodies to the virus are produced. [19] [20] Investigators have shown that viral loads are highest in semen and blood in the weeks before antibodies develop and estimated that the likelihood of sexual transmission from a given man to a given woman would be increased about 20-fold during primary HIV infection as compared with the same couple having the same sex act 4 months later. [21] Most people who are infected typically suffer from days to weeks of fever with or without muscle and joint aches, fatigue, headache, sore throat, swollen glands and sometimes rash. This "acute retroviral syndrome" is rarely diagnosed because it is difficult to distinguish from other very common ailments.

Main article: WHO Disease Staging System for HIV Infection and Disease in Adults and Adolescents

The Centers for Disease Control (CDC) in the United States reported a cluster of HIV infections in 13 of 42 young women who reported sexual contact with the same HIV infected man in a rural county in upstate New York between February and September 1996 [22]

The risk of oral sex has always been controversial. [23] Most of the early AIDS cases could be attributed to anal sex or vaginal sex. As the use of condoms became more widespread, there were reports of AIDS acquired by oral sex. [24]

Heterosexual transmission of HIV-1 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. Each 10 fold increment of seminal HIV RNA is associated with an 81% increased rate of HIV transmission. [25] During 2003 in the United States, 19% of new infections were attributed to heterosexual transmission [26]

The argument about the exact incidence of HIV transmission per act of intercourse is academic. Infectivity depends critically on social, cultural, and political factors as well as the biological activity of the agent. Whether the epidemic grows or slows depends on infectivity plus two other variables: the duration of infectiousness and the average rate at which susceptible people change sexual partners. [27]

Genetic susceptibility

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Diagram of the HIV virus

CDC has released findings that genes influence susceptibility to HIV infection and progression to AIDS. HIV enters cells through an interaction with both CD4 and a chemokine receptor of the 7 Tm family. They first reviewed the role of genes in encoding chemokine receptors (CCR5 and CCR2) and chemokines (SDF-1). While CCR5 has multiple variants in its coding region, the deletion of a 32-bp segment results in a nonfunctional receptor, thus preventing HIV entry; two copies of this gene provide strong protection against HIV infection, although the protection is not absolute. This gene is found in up to 20% of Europeans but is rare in Africans and Asians; researchers and scientists believe that the HIV virus had a similar viral shell as the virus which caused the black plague (1347-1350), leading to the decimation of one-third of the European population, possibly explaining why the CCR5-32 receptor gene is more prevalent in Europeans than Africans and Asians. Multiple studies of HIV-infected persons have shown that presence of one copy of this gene delays progression to the condition of AIDS by about 2 years. And it is possible that a person with the CCR5-32 receptor gene will not develop AIDS, although they will still carry the HIV virus.

Main article: HIV Disease Progression Rates

Treatment

There is currently no cure or vaccine for HIV or AIDS. Current optimal treatment 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). [28] 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. [29], [30].

There are several concerns about anti-retroviral regimens. The drugs can have serious side effects. Regimens can be complicated, sometimes requiring patients to take several pills at various times during the day, although most dosing and regimen schedules have been simplified greatly in recent years. If patients miss doses, drug resistance can develop [31]. 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.

The current guidelines for anti-retroviral therapy from the World Health Organization recommend that anti-retroviral therapy should start when a patient's CD4 count drops below 200/mm³, or an AIDS defining illness is diagnosed. The Department of Health and Human Services (DHHS), the federal agency responsible for overseeing HIV/AIDS healthcare policies in the United States, recommends that anti-retroviral therapy be started when the CD4 cell count is between 200 and 350/mm³. DHHS recommends that doctors should assess the viral load, rapidity in CD4 decline, and patient readiness while deciding when to begin treatment. [32]

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.

Alternative medicine

Ever since AIDS entered the public consciousness, various forms of alternative medicine have been used 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). 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.

Research

Origin

The official date for the beginning of the AIDS epidemic is marked as June 18, 1981, when the US 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. [33]

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. [34] Both HIV-1 and HIV-2 are of primate origin. The origin of HIV-2 has been established to be the sooty mangabey (Cercocebus atys), an Old World monkey of Guinea Bissau, Gabon, and Cameroon. The origin of HIV-1 is a chimpanzee subspecies: Pan troglodytes troglodytes.

Main article: AIDS origin

Circumcision

The Joint United Nations Programme on HIV/AIDS noted with considerable interest the results of a trial [35] [36] examining the potential link between male circumcision and a lower risk of HIV acquisition that were presented at the 3rd International AIDS Society Conference on HIV Pathogenesis and Treatment, held in Rio de Janeiro, Brazil in 2005. Although the trial shows promising protective effects of adult male circumcision in reducing HIV acquisition, UNAIDS emphasized that more research is needed to confirm the reproducibility of the findings of this trial and whether or not the results have more general application. UNAIDS believes that it is premature to recommend male circumcision as part of HIV prevention programmes. [37]

South African medical experts are concerned that the repeated use of unsterilised blades in the ritual circumcision of adolescent boys may be spreading HIV. [38]

Vaccine research

Main article: HIV vaccine

There is no vaccine for HIV; a June 2005 study estimates that $682 million is spent on AIDS vaccine research annually [39].

Alternative theories

Main article: AIDS reappraisal

A number of scientists and activists question the connection between HIV and AIDS, or the existence of HIV, or the validity of current testing methods.

References

Because of their length, the list of references used in developing this article is archived at Talk:AIDS/references

External links

• 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
• 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
• UNAIDS 2005 The Joint United Nations Programme on HIV/AIDS