What is HIV / AIDS

What is HIV / AIDS and Definition

An INFECTION with the human immunodeficiency virus (HIV) that ultimately results in the illness acquired immunodeficiency syndrome (AIDS). Though new HIV/AIDS infections are on the decline in the United States and other industrialized nations, HIV/AIDS remains endemic on the African continent.

HIV/AIDS spreads through contact with body fluids such as occurs with sexual contact (vaginal intercourse, anal intercourse, and oral sex) or through shared needles among intravenous DRUG users. Though previously infection through transfused BLOOD or blood products was a key means of infection, screening for HIV antibodies in donated blood supplies has significantly reduced this risk and infection through blood products is now uncommon.

Though there are numerous treatments for HIV/AIDS, there is no cure. HIV, the infection, nearly always progresses to AIDS, the illness, over the course of 5 to 20 years. Aggressive treatment can further manage the symptoms and complications of AIDS for years to sometimes decades. However, AIDS is ultimately fatal. AIDS does not itself cause death but instead so extensively damages the IMMUNE SYSTEM, the infection’s target, that the body cannot protect itself from infections or conditions such as cancer, which become the causes of death.

The Virus: HIV

The human immunodeficiency virus, HIV, is a retrovirus that exists in two known types, HIV-1 and HIV-2. Each infects the body in the same way and etches the same pathway to AIDS. HIV-1 is predominant in North America and Europe; HIV-2 is predominant in Africa, Southeast Asia, and China. HIV enters the body by attaching itself to a type of T-CELL LYMPHOCYTE called a CD4 cell (helper T-cell). CD4 cells direct the immune system’s response to infection and are integral to CELL-MEDIATED IMMUNITY. Once attached, the HIV virion, the essential structure of the VIRUS before it acquires a host cell, can infiltrate the cell without the immune system detecting its presence.

As a retrovirus, HIV uses reverse transcriptase, an enzyme, to instruct the CD4 cell’s RNA to replicate the virus’s RNA in place of the cell’s DNA. The cell then supports and replicates the virus, releasing new virions to infect additional CD4 cells. The entire process is quite stealthy. Therapeutic interventions are not quite of comparable stealth, though are getting closer to the mark. For example, ANTIVIRAL MEDICATIONS called nucleoside analogs can interject themselves into the process of reverse transcription, with the result that the cell produces “blank” DNA that fails to replicate the virus.

The Illness: AIDS

The ultimate outcome, at present, of HIV infection is the collapse of the immune system. Eventually the number of CD4 cells under HIV control is significantly greater than the number of CD4 cells under control of the immune system. Critical mass shifts and the immune system becomes deficient: It lacks the resources to rally against even the most minor of infections. Illness ranging from CANDIDIASIS (yeast infection) to AIDS-related lymphoma (a type of cancer) takes over. It is these illnesses, not HIV/AIDS, that causes death.

Symptoms of HIV/AIDS and Diagnostic Path

About two weeks after infection with HIV, mild flulike symptoms appear that last 10 to 14 days. Most people do not recognize these symptoms as HIV infection. After these initial symptoms resolve, there are no further symptoms until AIDS emerges. However, HIV antibodies become present in the body three to six months after infection (called seroconversion). Various tests are available to detect the presence of HIV antibodies, which confirm that a person has HIV infection (is HIVpositive). HIV infection is not the same as AIDS. AIDS is the end-stage outcome of HIV infection. At present the diagnostic criteria for the transition from HIV infection to AIDS is a CD4 count below 200 cells per cubic millimeter (mm3) and/or the development of an AIDS-defining clinical conditions (an illness that a healthy immune system would block from occurring).

HIV/AIDS: Treatment Options and Outlook

There are numerous treatment protocols for HIV/AIDS that extend both life expectancy and QUALITY OF LIFE. Early HIV infection does not require treatment beyond lifestyle measures to stay as healthy as possible. As the HIV begins to compromise the immune system, aggressive treatment with a regimen called HAART (highly active antiretroviral therapy), which combines three or more medications taken daily, can delay the progression of infection. Three factors influence the decision to begin HAART:

• CD4 count (the number of CD4 T-lymphocytes in the blood circulation) below 350 cells per cubic millimeter (mm3)
• viral load (the number of copies of HIV in the blood circulation) above 100,000 per milliliter (ml)
• presence of symptoms or an AIDS-defining clinical condition

Doctors wait to start HAART until these conditions exist because the antiretroviral drugs have potentially serious side effects, necessitating a careful balance between benefit and risk, and because once started, treatment is lifelong.

Regular blood tests to monitor CD4 counts and viral load determine how well a particular drug combination is working. Because drug toxicity and resistance are both problems with long-term HAART, it is sometimes necessary to change regimens.

Risk Factors and Preventive Measures

Numerous risk factors exist for HIV/AIDS. Key among them are

• unprotected vaginal intercourse, anal intercourse, or oral sex
• multiple sexual partners
• intravenous drug use with shared needles
• infection with SEXUALLY TRANSMITTED DISEASES (STDS) that have open sores, such as SYPHILIS and GENITAL HERPES
• vaginal intercourse during MENSTRUATION

Use of condoms with all sexual activity reduces the risk for spreading the virus but does entirely prevent infection. Pregnant women who are HIVpositive should discuss prophylactic treatment during PREGNANCY and for the infant after birth.

See also ANTIBODY; ANTIBODY-MEDIATED IMMUNITY; HIV/AIDS PREVENTION; SEXUAL HEALTH; SEXUALLY TRANSMITTED DISEASE (STD) PREVENTION.

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