Acquired immune deficiency syndrome (AIDS): The most severe manifestation of infection with HIV. An AIDS diagnosis is based on the presence of clinical symptoms, a patient's HIV viral load, and a CD4⁺ lymphocyte count at or below 200 cells per microliter in the presence of HIV infection. Persons living with AIDS often have infections of the lungs, brain, eyes, and other organs, and frequently suffer debilitating weight loss, diarrhea, and a type of cancer called Kaposi's sarcoma.

Addiction: A chronic, relapsing disease characterized by compulsive drug seeking and abuse and by long-lasting changes in the brain.

Antiretroviral drugs: Medications used to kill or inhibit the multiplication of retroviruses such as HIV.

Behavioral treatments: A set of treatments that focus on modifying thinking, motivation, coping mechanisms, and choices made by individuals.

CD4+ lymphocyte: A type of cell involved in protecting against viral, fungal, and protozoal infections. These cells normally stimulate the immune response, signaling other cells in the immune system to perform their special functions.

Cultural relevancy: The ability of an intended audience to view an intervention as applicable to their life circumstances.

Generational forgetting: Term to describe when knowledge of adverse consequences experienced by a particular generation or population is lost by a younger cohort. In this report, it refers to the diminished view of the dangers of HIV/AIDS among those 25 and younger.

Highly active antiretroviral therapy (HAART): A combination of three or more antiretroviral drugs used in the treatment of HIV infection and AIDS.

Hepatitis C virus (HCV): A virus that causes liver inflammation and disease. Hepatitis is a general term for liver damage and hepatitis C is the most common type of hepatitis found among those with HIV.

Human immunodeficiency virus (HIV): HIV is the virus that causes AIDS.

Injection drug use: Act of administering drugs using a hypodermic needle and syringe.

Opioid: A compound or drug that binds to receptors in the brain involved in the control of pain and other functions (e.g., morphine, heroin, oxycodone).

Pharmacological treatment: Treatment using medications.

Viral load: The quantity of HIV RNA (ribonucleic acid) in the blood. Research indicates that viral load is a better predictor of the risk of HIV disease progression than the CD4⁺ lymphocyte count. The lower the viral load, the longer the time to AIDS diagnosis and the longer the survival time. Viral load testing for HIV infection is used to determine when to initiate or change therapy.