What is HIV?

HIV stands for Human Immunodeficiency Virus. HIV eventually causes AIDS (see “What is AIDS?” below). In infected individuals, HIV is found in bodily fluids or blood and may be transmitted by:

• Having unprotected sexual intercourse with someone who is HIV-positive. Unprotected sex refers to sexual intercourse without the use of latex or polyurethane condoms.
• Sharing needles with someone infected with HIV
• Breast feeding and childbirth where an infected mother may transmit the virus to her child
• Any other exchange of bodily fluids from someone who is infected with HIV.

HIV is not transmitted through casual contact like hugging, kissing, or touching. The exchange of HIV-positive blood, semen, or vaginal secretions is necessary to contract the virus.

After infection, the virus multiplies in the body for several weeks or months, during which an individual can infect others but may not test HIV-positive. Once an individual’s immune system responds to the virus, the body will produce antibodies, and thus the person will test positive for HIV in a blood or oral mucus test (see “Diagnosis” for more information).

HIV operates by targeting T-cells of the immune system. T-cells, also known as “T-helper cells” or CD4 cells, are a special type of white blood cell that helps fight infections within the body. T-cells sense and signal other cells to fight bacteria, viruses, and other pathogens that cause disease. After penetrating a T-cell, HIV multiplies within the host cell until it bursts, releasing the replicated viruses into the bloodstream to infect other T-cells. This cycle can significantly lower a person’s T-cell count.

Upon infection, most people will experience flu-like symptoms such as fever, headache, soreness, swollen lymph glands, or rash. Some infected individuals do not experience these early symptoms. After infection, many people appear healthy for a number of years. During this time, however, the virus damages the immune system by destroying T-cells. The progress of the disease is measured by monitoring the CD4 cell count in the blood. Normally, a healthy individual will have between 800 and 1,200 CD4 cells per microliter of blood.

If an individual’s T-cell count falls below 200 CD4 cells per microliter of blood, or if the CD4 cell count is less than 14 percent of the total number of lymphocytes (white blood cells) in the body, then he or she is diagnosed with AIDS. A person can also be diagnosed with AIDS if he or she develops an “opportunistic infection.” An opportunistic infection is an infection that takes advantage of weaknesses in the body’s immune defenses and does not normally occur in a healthy individual.

Currently, there is no cure for HIV. Once infected, individuals carry the virus for the rest of their lives. There are drugs, however, that can slow down the virus’s progress and allow those infected to live a long, healthy life (see “Treatment Overview“).

What is AIDS?

AIDS stands for Acquired Immune Deficiency Syndrome. AIDS is caused by the human immunodeficiency virus (HIV), a virus that targets and destroys the immune system.

A person can live a healthy life for many years after becoming infected with HIV. Over time, however, HIV kills a type of immune cell called CD4 cells, eventually leading to a non-functional immune system. When a person’s CD4 count, otherwise known as a T-cell count, becomes less than 200 or less than 14 percent of the total number of lymphocytes (white blood cells) in the body, the person is diagnosed with AIDS.

An individual can also be diagnosed with AIDS if he or she develops a rare “opportunistic infection”. Opportunistic infections are infections that take advantage of weaknesses in the immune system and do not normally occur in healthy individuals. These infections occur because the immune system is no longer capable of fighting off the bacteria and viruses that cause them. Some of the most common opportunistic infections are:

• Candidiasis (thrush)
• Herpes simplex virus
• Pneumocystis pneumonia
• Kaposi’s sarcoma

AIDS patients are also more susceptible to malaria, tuberculosis, and other illnesses. If untreated, these opportunistic infections will eventually lead to death, as the body lacks T-cells to help fight them. (See “Signs & Symptoms” for more information on AIDS and opportunistic infections).

There is currently no cure for AIDS or for HIV. However, there are drugs that can slow down the progress of the HIV virus and even reverse immune damage, allowing an infected individual to live a long, healthy life (see “Treatment Overview“).

Who is at Risk? »