HIV/AIDS Center

AIDS has become a global epidemic. More than twenty years have passed since the first reports of the disease and 47 million people have been infected during that time. The Centers for Disease Control and Prevention (CDC) has estimated that about 800,000 Americans are living with HIV/AIDS. Treatments are constantly improving and are prolonging life but unfortunately high-risk behavior is increasing in some communities.

What is the difference between HIV and AIDS?

HIV (Human Immunodeficiency Virus) damages or destroys the cells of the immune system, making the body less able to fight infection and more susceptible to often life threatening opportunistic infections.

The term AIDS (Acquired Immunodeficiency Syndrome) refers to the latter stages of HIV infection. Most individuals infected with HIV will progress to AIDS if not treated; however, there are very small numbers of patients who develop AIDS very slowly or not at all.

How is HIV Diagnosed?

HIV is diagnosed by testing the blood for the presence of antibodies to the virus. Most often, this is performed using a simple blood test known as an enzyme-linked immunosorbent assay (ELISA) screening test.

Unfortunately, HIV tests aren't accurate immediately after infection because it usually takes 6 to 12 weeks for the body to develop antibodies. In rare cases it can take up to 6 months for an HIV test to become positive.

If this test is positive (i.e. if there are HIV antibodies present in the blood) the test will be repeated. If the second test is also positive for HIV antibodies, another blood test, called a Western blot test, will confirm the result through the detection of HIV proteins.

The Western blot test is important because non-HIV antibodies can cause a false positive result on the ELISA test. Combining the two types of tests helps ensure that the results are accurate. If all three tests are positive a diagnosis of HIV infection will be given.

Once a person is diagnosed with HIV, a further blood test (a viral load test, which measures the amount of virus in the blood) will help determine the probable progression of the disease. Viral load tests are also used to manage the drug treatments that will be administered following diagnosis.

How is AIDS diagnosed?

AIDS is diagnosed when a person is HIV positive and either has a CD4 lymphocyte (T-cell) count of less than 200 or develops one of the AIDS-defining diseases.

For further information see HIV and AIDS: Symptoms and Complications

How does the HIV virus affect the immune system?

When a foreign organism enters the body, it is attacked by white blood cells and antibodies in a response coordinated by CD4 lymphocytes (these are a type of white blood cell and are also known as T-cells). When the body is infected with HIV, the HIV virus attaches to the CD4 lymphocytes and enters the cells. Once inside, the virus inserts its own genetic material into the CD4 lymphocytes and then replicates itself.

When the new copies of the virus break out of the host cells and enter the bloodstream, they search for other cells to attack. The cycle repeats itself again and again. In the process, more than 10 billion new HIV particles are produced every day. To counter this huge virus production, the immune system turns out as many as 2 billion new CD4 cells daily.

Eventually, the virus wins. The number of CD4 cells progressively decreases and the body develops severe immune deficiency whereby it is no longer able to effectively fight off viruses and bacteria that cause disease. AIDS is the final and most serious stage of HIV disease, in which the signs and symptoms of severe immune deficiency have developed.

How is HIV transmitted?

HIV is transmitted through body fluids:

• Sexual contact with an HIV-infected partner
• Infected blood - rare nowadays due to thorough screening
• Shared needles and syringes contaminated with infected blood
• Accidental needle stick injury
• Mother to child transmission (via pregnancy or breast-feeding)
• In rare cases the virus may be transmitted through organ or tissue transplants, through artificial insemination with donated semen, or through un-sterilized dental or surgical equipment.

HIV is not transmitted via ordinary contact (hugging, dancing, sneezing, talking, touching, or shaking hands) with someone who has HIV or AIDS. HIV is not transmitted through sweat, tears or saliva; or through sharing food, utensils, towels, bedding, a swimming pool, telephone or toilet seat with someone who has the virus. HIV is not transmitted through bedbugs or mosquitoes.