Glossary

Acquired Immunodeficiency Syndrome (AIDS): A disease of the immune system due to infection with HIV. HIV destroys the CD4 T lymphocytes (CD4 cells) of the immune system, leaving the body vulnerable to life-threatening infections and cancers. Acquired immunodeficiency syndrome (AIDS) is the most advanced stage of HIV infection. To be diagnosed with AIDS, a person with HIV must have an AIDS-defining condition or have a CD4 count less than 200 cells/mm3 (regardless of whether the person has an AIDS-defining condition).

Gay-Related Immune Deficiency (GRID): A term used in the early days of the epidemic by healthcare professionals, researchers, and journalists to describe the outbreak of unusual illnesses among gay men. The term, rooted in the mistaken belief that only gay-bisexual men are experiencing the immune deficiencies, will create long-term challenges for heterosexual men, women, and children—many of whom will not be diagnosed with AIDS because they do not fit the “profile.” The term is officially discarded in September 1982 when the Centers for Disease Control chooses the term “AIDS” (for “Acquired Immune Deficiency Syndrome) as a more accurate—and neutral—term to describe the new cluster of illnesses. But the perception that AIDS is a disease strictly of gay men will linger indefinitely.

Hemophilia: A rare blood-clotting disorder that is usually inherited and most often affects males. The main symptom of hemophilia is prolonged bleeding either spontaneously or after an injury or accident.

Human Immunodeficiency Virus: The virus that causes AIDS, which is the most advanced stage of HIV infection. HIV is a retrovirus that occurs as two types: HIV-1 and HIV-2. Both types are transmitted through direct contact with body fluids containing HIV, such as blood, semen, and vaginal fluids, or from a mother who has HIV to her child during pregnancy, labor and delivery, or breastfeeding (through breast milk).

Immunosuppression: Occurs when the body's ability to mount an immune response to fight infections or disease is reduced. It may be caused by certain diseases, such as HIV, or by radiotherapy or chemotherapy. Immunosuppression may also be deliberately induced by drugs used to prevent rejection of transplanted organs.

Kaposi’s Sarcoma (KS): A rare type of cancer characterized by the abnormal growth of cells that line lymph and blood vessels. KS causes red or purple patches of tissue (lesions) to grow under the skin and in the lining of the mouth, nose, and throat. Lesions may also develop in the digestive tract, liver, or lungs. KS generally occurs in people with weakened immune systems. In people with HIV, KS is an AIDS-defining condition. It is named for Hungarian dermatologist Dr. Moritz Kaposi, who first reported the condition in 1872.

Pentamidine: A drug used to treat several infectious diseases caused by microorganisms, including African trypanosomiasis [sleeping sickness] and leishmaniasis. In the late 1970s and early 1980s, injectable/intravenous pentamidine was the drug of choice for treating Pneumocystis pneumonia (PCP), a life-threatening illness that generally affected only people with severely compromised immune systems, like those with advanced forms of cancer or those who had had organ transplants and required immunosuppresive drugs to keep their bodies from rejecting their new organs. Because PCP was so rare, the Centers for Disease Control was the sole distributor for the small amount of pentamidine available in the United States. A sudden surge in requests for the drug for people with no known underlying immune disorder was the first indication to CDC that a new epidemic was brewing. Beginning in the late 1980s, healthcare providers start treating people with AIDS with aerosolized pentamidine to prevent PCP, as well as to treat it.

Pneumocystis pneumonia (PCP): A lung infection caused by the fungus Pneumocystis jirovecii. Symptoms include a cough (often mild and dry), fever, and shortness of breath. The fungus is common in the environment and does not cause illness in healthy people. Most people who get Pneumocystis pneumonia have weakened immune systems due to HIV/AIDS, cancer treatments, or organ transplants. In people living with HIV, PCP is an AIDS-defining condition. (Note: For the first 20 years of the HIV epidemic, the infection is known as Pneumocystis carinii pneumonia, and this timeline follows that convention. For the history behind the name change, see the PDF for 1981.)

Surveillance Case Definition: A set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient's health needs.