Glossary of Important HIV Terms

This glossary is a great place to get started adjusting to some of the complicated language used to discuss HIV. This is not a thorough overview of HIV, how HIV works in the body, how HIV medications work, transmission and prevention of HIV infection, or health conditions associated with HIV; visit our Who, What, Why of HIV section and the Helpful Web Links (for further research) section to delve deeper.

The Basics:

HIV (Human Immunodeficiency Virus) – the virus that causes AIDS. HIV gradually weakens a person’s immune system over time; however, with the proper medications and medical care, a person living with HIV can now lead a long, healthy life. Someone living with HIV who sees their doctor regularly and takes the right medications may never have HIV progress to AIDS, but if HIV is left untreated, it can cause grave damage to the immune system and make a person more likely to get serious, sometimes life-threatening, infections. There is currently no cure for HIV but there are effective medications to treat HIV and keep it under control so that damage to the immune system can be slowed, stopped, or even reversed. HIV progresses in stages:

Primary HIV Infection (a.k.a. Acute HIV Infection) – the first stage of HIV infection. During this early period of HIV some HIV tests may not yet detect the infection. Even though an HIV test may not yet detect the infection, someone in the early stage of HIV infection can still transmit the virus to others. The amount of HIV in the body increases rapidly during this phase, which typically lasts for a few weeks to a couple months. Most, but not all, people newly infected with HIV develop a flu-like illness in reaction to HIV within a few weeks of their exposure.

Asymptomatic HIV – After the acute/primary infection phase, most people with HIV feel well and have no particular symptoms of HIV. This phase typically lasts for a number of years, though that can vary from person to person. During this phase, HIV remains present in the body and, typically, slowly weakens the immune system although a person may not feel that anything is wrong.

Symptomatic HIV –the longer HIV remains untreated, the more likely a person is to begin experiencing symptoms caused by HIV. Some people have diarrhea, headaches, skin conditions, swollen lymph glands, unusual or prolonged infections or may begin to have trouble with fatigue and weight loss. Untreated HIV also increases the risk of heart disease, some cancers, and other illnesses over time.

AIDS – Acquired Immune Deficiency Syndrome – this is the name of the most advanced stage of HIV, when a person’s immune system has been seriously damaged by HIV infection. A person with AIDS is at higher risk of getting serious, life-threatening infections. People who have AIDS may need medications that help to prevent certain common infections (called opportunistic infections) in addition to normal HIV medications while their immune system is weak. Standard HIV treatments are still effective against HIV at this stage and they are essential to improving the health of someone living with AIDS; however, the immune system may be slower to improve in response to treatments when started at this stage than when the treatments can be started in an earlier stage.


ART (a.k.a. ARVs or HAART) – AntiRetroviral Therapy is a combination of medications that treat HIV and keep it under control. ART stops HIV from reproducing in the body, which helps keep someone living with HIV healthy. ART can even reverse damage already done to the immune system for many people. When a person is prescribed ART, they will take a combination of at least three different medications, though these are often co-formulated so that a person only has to take one or two pills per day. ART is recommended for every person living with HIV, regardless of how healthy or weak a person’s immune system is or how long they have had it.

PEP (Post-Exposure Prophylaxis) – a course of HIV-medications (see ART, above) that a person takes for about one month immediately following an exposure to HIV. Starting on PEP as soon as possible (within 72 hours is recommended, and the sooner the better) and continuing on PEP for the full course can reduce that person’s risk of acquiring an HIV-infection from the exposure. PEP is regularly used in cases where healthcare workers get an accidental needle stick with a used needle; however, PEP can also be used for other non-occupational exposures such as condomless sex or exposure to blood via drug injection or other sources.

PrEP (Pre-Exposure Prophylaxis) – a medication that is recommended for HIV-negative persons at risk for HIV-infection. If taken every day, PrEP can reduce a person’s risk for acquiring HIV by more than 90%. PrEP works by preventing HIV from being able to replicate inside the body, so even if someone who takes PrEP every day gets exposed to HIV, an infection should not be able to start.

Prophylaxis – means taking medications to prevent infections from developing when a person’s immune system is weak and less able to fight off infections on its own (usually once a person’s HIV infection has reached the stage called AIDS). Prophylaxis can improve a person’s quality of life and survival when their immune system is weak. If effective HIV treatment raises a person’s CD4 count above certain thresholds, prophylaxis can be stopped.

Lab (Blood) Tests:

CD4 Count (a.k.a. T-Cell Count) – a lab test that measures the number of CD4 cells in a microliter of blood. A CD4 count provides a general idea of how healthy a person’s immune system is. CD4 cells are a type of white blood cell and are a part of a person’s immune system; they play an important role in fighting off infections. The higher a person’s CD4 count is, the healthier their immune system is. Because HIV kills CD4 cells, people living with HIV tend to see their CD4 count decrease over time; however, when a person is on HIV medications and their Viral Load is “undetectable,” CD4 counts can remain stable or even increase over time.

When a person’s CD4 count drops below 200 cells per microliter, their immune system has been seriously damaged and they are more likely to get certain infections.

Viral Load (VL) – a lab test that measures how much HIV is present in a blood sample. A “normal” VL result for an HIV-positive person not yet on HIV medications can vary a lot from person to person. A higher Viral Load (VL) result means that there is more HIV present in the body, harming the immune system. A lower VL result means that there is less HIV is present in the body, which reduces damage to the immune system. When a person starts HIV medications, their VL should decrease so much that their VL can become “undetectable” (see “undetectable,” below).

“Undetectable” – having an undetectable Viral Load (VL) means that there is so little HIV virus in a blood sample that it cannot be detected by a standard test for the virus. At our clinic, having an undetectable viral load means that there is no HIV detected in the sample.  Patients may also have the result of “less than 40 copies” which means there is a small signal, so small that it cannot be quantitated, and is fewer than 40 copies of HIV in a milliliter of blood. When someone is “undetectable,” that means that HIV is not actively reproducing in the body or actively doing damage to the immune system. It also means that it is unlikely that the person can pass HIV on to someone else through sex or from mother to child. It does NOT mean that the person is cured of HIV. If a person who is “undetectable” stops taking their HIV medications, their VL will normally begin to increase within days to weeks of stopping.

Other Terms:

Opportunistic Infections (a.k.a. OIs) – certain infections that are much more common in people who have weak immune systems. Examples of OIs that are seen in people living with AIDS include thrush (yeast infection in the mouth or throat), certain types of pneumonia, herpes sores that do not go away, and Tuberculosis, among many others. In addition, there are other “AIDS Defining Illnesses,” including cancers that are more common in people with AIDS (such as Kaposi’s Sarcoma, lymphoma, and invasive cervical cancer).

Resistance – HIV can develop resistance to antiretroviral medication just like bacteria can develop resistance to antibiotics. Resistance means that a medication (drug) which would normally be able to treat and kill the HIV virus is no longer effective at killing the virus. The most common way a person acquires drug resistant HIV is by not taking their ART medications faithfully (see ART above). Another way a person can acquire drug-resistant HIV is through sexual contact with a partner who has a drug-resistant strain of HIV. Oftentimes a test, called a “genotype resistance test,” can be done to see if resistant virus is present. These tests help a person’s provider choose medications that are still effective in treating resistant HIV; however, if more and more resistance develops, it becomes more difficult to find a combination of medications that will control HIV successfully.

“Superinfection” – is the concept of infection of an already HIV-positive person with a second strain of HIV. The superinfection can be with a more aggressive strain of HIV or a strain of HIV that already has some drug resistance. Keep in mind that different strains of HIV, including strains which have drug resistance, can be passed sexually from person to person, so safer sex can be important even between partners who are already HIV-positive.

Stigma – a set of negative and unfair beliefs that society or a group of people have about something. People living with HIV today can suppress HIV with medications and live a long, healthy life; however, there is still widespread fear of HIV and poor understanding about how it can and cannot be spread, who can be affected by HIV, and what an HIV diagnosis means. Examples of HIV stigma include an HIV-positive person feeling shame about their HIV-diagnosis; an HIV-positive person losing work, friendships, or romantic relationships when others find out about their HIV-status; or the belief that having HIV means that a person is dying.  Unfortunately, many people living with HIV still face discrimination or personal hardship because of HIV stigma. Stigma about HIV can make it very difficult for some people to tell others about their HIV diagnosis. For others, HIV stigma can make it difficult to even seek out an HIV test. Ask Madison Clinic staff for resources to help educate yourself or others about HIV, or for referrals to organizations that help fight stigma by providing social support, information, or advocacy on behalf of people living with HIV.