HIV Care and Prevention Program

HIV/AIDS Glossary

Here is a list of commonly used medical terms related to HIV care. Never hesitate to ask your medical care team if you have questions about a term.

If you cannot find what you are looking for, there is a detailed list of terms at AIDSinfo, a service of the U.S. Department of Health and Human Services.


The degree to which a patient follows the medical advice given to them by their medical provider, especially related to taking medications. A patient is adhering to the medication plan if they take medications exactly as prescribed.

AIDS (Acquired Immune Deficiency Syndrome)

Though named a syndrome (cluster of symptoms without an easily identifiable cause), it is now well understood that AIDS is a disease state with a known cause - the Human Immunodeficiency Virus (HIV). It is often characterized by infections that take advantage of an immune system that has been weakened by fighting HIV.

Antiretroviral drugs (ARVs)

A drug used to interrupt the ability of a particular kind of virus, called a retrovirus, to make copies of itself. Retroviruses, like HIV, become part of the genetic makeup of the cells that they infect. The four different classes of antiretrovirals each interrupt the replication at different points in the process. This is why antiretrovirals from more than one class are often combined to fight HIV.

Antiretroviral Therapy (ART)

Antiretroviral therapy refers to the combination of antiretroviral drugs used to treat HIV.


When an HIV patient is not showing any outward signs or symptoms of having the disease. 


The right or expectation that information will be kept private.

CD4 count

CD4 cells (also known as T-cells) activate the body's immune system. Medical providers use a CD4 count to see how well a patient's immune system is functioning. The more CD4 cells you have, the better, as it means the body is able to fight off infections.


When a patient has two or more viruses at the same time. For example: someone who has HIV and Hepatitis C.

Drug resistance

 When a virus becomes resistant to a drug that was previously effective. Occurs when HIV continues to make copies of itself while someone is taking antiretrovirals. A virus naturally makes mistakes in the process of copying itself. To treat HIV, a potent combination of antiretrovirals is used to keep the replication as low as possible. When the antiretrovirals do not put enough pressure on the virus - commonly due to missing doses - the virus is able to make more copies, increasing the chances that some of the copies will be resistant to the drugs that are present. Those drugs then become less able to suppress the virus because it is resistant to them.

Human Immunodeficiency Virus (HIV)

 HIV is the virus that causes AIDS. It weakens the immune system by using the body's infection-fighting cells to manufacture copies of itself. 

NNRTI (Non-Nucleoside Reverse Transcriptase Inhibitor) 

One of four classes of anti-HIV drugs. Includes Viramune (nevirapine), Sustiva (efavirenz) and Rescriptor (delavirdine). Drugs in this class prevent HIV from making copies of itself by binding to an enzyme (reverse transcriptase) of the virus that is used in the replication (copying) process.

Opportunistic Infection (OI)

Infections that occur more often or are more severe in people with weakened immune systems than in people with healthy immune systems. HIV-related OIs include pneumonia, Salmonella, thrush, toxoplasmosis, and tuberculosis (TB).

Post-Exposure Prophylaxis (PEP)

Short - term treatment with HIV medications started within 72 hours after potential exposure to HIV that can help reduce the chance of HIV infection.

Pre-Exposure Prophylaxis (PrEP)

Pre-exposure prophylaxis is a strategy of taking daily antiretroviral (ARV) medications in order to lower a person's chance of getting infected with HIV.


Also known as a CD4 cell. See "CD4 Count."


When the amount of HIV in the blood is too low to be detected with a viral load (HIV RNA) test. Antiretroviral (ARV) drugs may reduce a person's viral load to an undetectable level; however, that does not mean the person is cured. Some HIV, in the form of latent HIV reservoirs, remain inside cells and in body tissues.

Viral Load

The amount of HIV in a patient's blood. If viral load is high, CD4 count is low.

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