The language of HIV/AIDS is often difficult to understand - here are some definitions for commonly used terms.

What is HIV?

HIV (human immunodeficiency virus) is the virus that causes AIDS.

This virus may be passed from one person to another when infected blood, semen, or vaginal secretions come in contact with an uninfected person's broken skin or mucous membranes*. In addition, an infected pregnant woman can pass HIV to her baby during pregnancy or delivery, as well as through breast-feeding. People with HIV have what is called HIV infection. Some of these people will develop AIDS as a result of their HIV infection.

* A mucous membrane is wet, thin tissue found in certain openings to the human body. These can include the mouth, eyes, nose, vagina, rectum, and opening of the penis.

What is AIDS?

AIDS stands for Acquired Immunodeficiency Syndrome.

• Acquired means that the disease is not hereditary but develops after birth from contact with a disease causing agent (in this case, HIV).
• Immunodeficiency means that the disease is characterised by a weakening of the immune system*.
• Syndrome refers to a group of symptoms that collectively indicate or characterise a disease. In the case of AIDS this can include the development of certain infections and/or cancers, as well as a decrease in the number of certain cells in a person's immune system.

* An immune system is a collection of mechanisms within an organism that protects against infection by identifying and killing pathogens and tumor cells. It detects pathogens ranging from viruses to parasitic worms and distinguishes them from the organism's normal cells and tissues. (Source: Wikipedia)

A diagnosis of AIDS is made by a physician using specific clinical or laboratory standards.

What are ARVs?

ARVs stands for Antiretrovirals. These are medications that have specific activity against HIV and reduce HIV's ability to damage the immune system. When taken appropriately and in combination (see "HAART") they can lead to a healthier and longer life in patients with HIV.

What is ART?

ART stands for Antiretroviral Treatment, in other words treatment using Antiretroviral drugs.

What is a CD4 count?

This is a measure of the strength of the immune system. HIV continually kills CD4 cells. Over time, the body can not replace these lost CD4 cells and their number declines. When this happens the body will be more susceptible to infections. A normal CD4 count is 1000. The body starts to get more frequent common infections at around a count of 400. At around a CD4 count of 200 the body becomes susceptible to many unusual infections. It is best to start medications for HIV before the CD4 count drops below 200 to prevent these infections from developing.

What is a Viral load?

This is a measure of how much HIV is found in the blood. The viral load can predict how fast the virus will damage the immune system. In treated patients, the viral load is an accurate measure of how effective treatment is. It should be noted that patients with an "undetectable" viral load can still transmit HIV to others. This is because the viral load can vary from one day to another day (be undetectable one day and be detectable the next), and the virus may be present in high levels in genital fluids when the virus is not detectable in the blood.

What does "HAART" stand for?

HAART stands for highly active antiretroviral therapy. HAART refers to the combination of HIV medications currently used to treat HIV. HAART does not cure HIV but can reduce the level of HIV in the body to very low levels and prevent destruction of the immune system. In order for the medications to remain effective, medications need to be taken as directed by your doctor. (See "resistance")

What does Prophylaxis mean?

This term refers to medications taken to prevent infections from developing as the immune system falters. Prophylaxis can improve the HIV patient's quality of life and extend survival. If effective HIV treatment raises the CD4 count above certain thresholds, prophylaxis can be stopped.

What does Resistance mean?

Resistance means that the HIV virus is no longer killed by a particular treatment (drug). The most common way a patient acquires drug resistant HIV is by not taking his medications faithfully. Often a test can be done to see if resistant virus is present. These tests help your provider choose medications that still may be effective in treating resistant HIV. However, with increasing resistance, it gets harder and harder to find a combination of medications that will control HIV successfully.

What are Sexually transmitted diseases (STDs)?

STD's are a large group of infections that can be spread via sexual contact. The most common are chlamydia, genital warts, gonorrhea, hepatitis B virus, herpes, HIV, and syphilis.

What is an Opportunistic Infection?

Opportunistic Infections are illnesses caused by various organisms, some of which usually do not cause disease in persons with normal immune systems. Persons living with advanced HIV infection suffer opportunistic infections of the lungs, brain, eyes, and other organs. Opportunistic infections common in persons diagnosed with AIDS include Pneumocystis carinii pneumonia; Kaposi's sarcoma; cryptosporidiosis; histoplasmosis; other parasitic, viral, and fungal infections; and some types of cancer.

What is a "Superinfection"

This is the concept of infection of an already HIV-infected person with a second strain of HIV. The superinfection can be with a more aggressive strain of HIV.

What are "T cells"?

T cells (T Lymphocytes) are white blood cells, derived from the thymus gland, that participate in a variety of cell-mediated immune reactions.

What is Seroconversion?

Seroconversion is the development of antibodies to a particular antigen. When people develop antibodies to HIV, they "seroconvert" from antibody-negative to antibody-positive. It may take from as little as one week to several months or more after infection with HIV for antibodies to the virus to develop. After antibodies to HIV appear in the blood, a person should test positive on antibody tests. See Incubation Period; Window Period.

What is the Incubation Period?

This is the time interval between the initial infection with a pathogen (eg, HIV) and the appearance of the first symptom or sign of disease.

What is the Window Period?

This is the time from infection with HIV until detectable seroconversion. This can be as little as 10 days.