The time taken for the amount of drug in the body (or its concentration in plasma or within cells) to be reduced by 50% as a result of metabolism and excretion.

T cells are lymphocytes (white blood cells) that are formed in the thymus and are part of the immune system. They have been found to be abnormal in persons with AIDS. The normal ratio of helper T cells (CD4+ cells) to suppressor T cells (CD8+ cells) is approximately 2:1. This ratio becomes inverted in persons with AIDS but also may be abnormal for a host of other temporary reasons.

Enlargement of the liver.

A group of viruses that includes herpes simplex virus type 1 (HSV-1 or HHV-1) and 2 (HSV-2 or HHV-2), varicella-zoster virus (VZV or HHV-3), Epstein-Barr virus (EBV or HHV-4), cytomegalovirus (CMV or HHV-5), human herpesvirus types 6 and 7 (HHV-6, HHV-7) and Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8). Herpesviruses may act as opportunistic pathogens and/or cofactors in HIV pathogenesis.

The name given to treatment regimens recommended by leading HIV experts to aggressively suppress viral replication and progression of HIV disease. The usual HAART regimen combines three or more different drugs, such as two nucleoside reverse transcriptase inhibitors (NRTIs) and a protease inhibitor, two NRTIs and a non-nucleoside reverse transcriptase inhibitor (NNRTI) or other combinations. These treatment regimens have been shown to reduce the amount of virus so that it becomes undetectable in a patient's blood.

A fungal infection, commonly of the lungs, caused by the fungus Histoplasma capsulatum. This fungus is commonly found in bird and/or bat droppings in the Ohio and Mississippi Valley region, the Caribbean Islands, and in Central and South America. It is spread by breathing in the spores of the fungus. Persons with severely damaged immune systems, such as those with AIDS, are vulnerable to a very serious disease known as progressive disseminated histoplasmosis.

Human immunodeficiency virus. In an untreated infected person suppresses the immune system, leading to severe infections and AIDS.

The rate of virus replication that stabilises and remains at a particular level in each individual after the period of primary infection.

An organism (e.g. human) in which another organism (e.g. HIV) lives and reproduces.

The body's potent mechanisms for containing HIV, including immune system cells, called CD8+ T cells, which may prove more effective than any antiretroviral drug in controlling HIV infection.

The retrovirus isolated and recognised as the aetiologic (i.e., causing or contributing to the cause of a disease) agent of AIDS. HIV-1 is classified as a lentivirus in a subgroup of retroviruses.

A virus closely related to HIV-1 that has also been found to cause AIDS. It was first isolated in West Africa. Although HIV-1 and HIV-2 are similar in their viral structure, modes of transmission, and resulting opportunistic infections, they have differed in their geographic patterns of infection.

The virus that causes genital warts and is linked to cervical dysplasia and cervical cancer. The virus can be transmitted through sexual contact. HPV is a frequently seen infection in women with HIV/AIDS.

Abnormally high levels of immunoglobulins in the blood. Common in persons with HIV.