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Glossary of HIV/AIDS Terms

for Health Care Providers

Glossary of HIV/AIDS Terms

Hairy leukoplakia

See Oral hairy leukoplakia (OHL).

Harm reduction

A prevention activity that aims to provide services to people with HIV and their sex and needle-sharing partners so they can reduce their risk of infection or, if already infected, prevent transmission of HIV to others. It also involves helping partners gain earlier access to individualized counseling, HIV testing, medical evaluation, treatment, and other prevention and support services.


Health care worker.

Helper T cells

Lymphocytes bearing the CD4 marker that are responsible for many immune system functions, including turning antibody production on and off.

See CD4 (T4) or CD4+ cells.

Helper/Suppressor ratio (of T cells)

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 (also known as CD4+ T cells) to suppressor T cells (also known as CD8+ T cells) is approximately 2 to 1. This ratio becomes inverted in persons with AIDS but also may be temporarily abnormal for other reasons.


A laboratory measurement of the percentage of packed red blood cells in a given volume of blood. In women, red blood cells are normally 37 to 47 percent of their blood, and in men, red blood cells are normally 40 to 54 percent of their blood.


Poisonous to the blood or bone marrow.

Hemoglobin (HGB)

The red, iron-based pigment in red blood cells that enables them to transport oxygen; normal hemoglobin values are 14-18 g/dL in men and 12-16 g/dL in women. Normal values in resource-poor countries may be lower.


The rupture of red blood cells.


Pertaining to the liver.


An inflammation of the liver. May be caused by bacterial or viral infection, parasitic infestation, alcohol, drugs, toxins, or transfusion of incompatible blood. Although many cases of hepatitis are not a serious threat to health, the disease can become chronic and can sometimes lead to liver failure and death. There are four major types of viral hepatitis: A, B, C, and D.

Hepatitis A

Caused by infection with the hepatitis A virus, which is spread by fecal-oral contact.

Hepatitis B

Caused by infection with the hepatitis B virus (HBV), which is most commonly passed to a partner during sexual intercourse, especially during anal sex, as well as through sharing of drug needles.

Hepatitis C

Caused by infection with the hepatitis C virus, which is most commonly passed through sharing of drug use equipment; it also can be passed to a partner during sexual intercourse, especially during anal sex. Approximately 40% of patients infected with HIV are also infected with the hepatitis C virus (HCV), mainly because both viruses share the same routes of transmission.


Enlargement of the liver.


Abnormal enlargement of both the liver and the spleen.


Liver damage due to toxic effects of poisons or drugs. Early damage is usually detected by measuring liver enzymes.

Herpes simplex virus 1 (HSV-1)

A virus that causes cold sores or fever blisters on the mouth or around the eyes, and can be transmitted to the genital region. Stress, trauma, other infections, or suppression of the immune system can reactivate the latent virus.

Herpes simplex virus 2 (HSV-2)

A virus causing painful sores of the anus or genitals that may lie dormant in nerve tissue. It can be reactivated to produce symptoms. HSV-2 may be transmitted to a newborn during birth from an infected mother, causing retardation and/or other serious complications.

Herpes varicella-zoster virus (VZV)

The varicella virus causes chickenpox in children and may reappear in adults as herpes zoster. Also called shingles, herpes zoster consists of very painful blisters on the skin that follow nerve pathways.

Herpes viruses

A group of viruses that includes herpes simplex type 1 (HSV-1), herpes simplex type 2 (HSV-2), Cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella-zoster virus (VZV), human herpes virus type 6 (HHV-6), and HHV-8, a herpes virus associated with Kaposi sarcoma. See entries under names of some of the individual viruses.

Herpes zoster

A painful infection with the varicella virus that normally causes chickenpox. The virus may be dormant for many years in the cells of the nervous system. When reactivated, it appears on the skin in various locations as painful sores. Also called shingles.

Highly active antiretroviral therapy (HAART)

An older name for antiretroviral therapy (ART).

See Antiretroviral therapy (ART).

High-risk behavior

A reported sexual, injection drug use, or other non-work-related HIV exposure that might put a patient at high risk of acquiring HIV infection.


A fungal infection, commonly of the lungs, caused by the fungus Histoplasma capsulatum. This fungus is commonly found in bird and bat droppings. It is spread by breathing in the spores of the fungus. Persons with severely damaged immune systems, such as those with AIDS, are susceptible to a very serious disease known as progressive disseminated histoplasmosis.

HIV prevention counseling

Provision of information on how HIV is transmitted, how an individual becomes infected, and how to prevent infection. Encompasses all modes of transmission including sexual activity (heterosexual, homosexual and bisexual), intravenous drug use, mother-to-child transmission, breast feeding, accidental exposure from an infected patient, and HIV-infected blood transfusion.

HIV set point

The point at which the level of virus stabilizes and remains at a particular level in each individual after the period of primary infection.

HIV viral load

See Viral load test.

HIV-associated dementia (HAD)

Previously referred to as AIDS dementia complex (ADC). A degenerative (destructive) neurological condition attributed to HIV infection, characterized by a group of clinical presentations including loss of coordination, mood swings, loss of inhibitions, and widespread inability to think. It is the most severe manifestation of HIV-associated neurocognitive disorder (HAND) and usually is seen in persons with untreated or inadequately treated late-stage HIV disease.

HIV-associated neurocognitive disorder (HAND)

A spectrum of central nervous system abnormalities caused by HIV infection. These can range from asymptomatic impairment of thinking processes to severe dementia.

HIV-Exposed Infant

An infant born to a mother infected with HIV and exposed to HIV during pregnancy, childbirth, or breast feeding.

Hodgkin disease

A progressive cancer of the lymphatic system. Symptoms include lymphadenopathy, wasting, weakness, fever, itching, night sweats, and anemia. Treatment includes radiation and chemotherapy.

Home sample collection test

A test kit that a consumer purchases and uses to collect blood (or other body fluid) to send away for testing.


Pertaining to sexual activity with a person of the same sex.


An active chemical substance formed in one part of the body and carried in the blood to other parts of the body where it stimulates or suppresses cell and tissue activity.

Host factors

The body's mechanisms for containing HIV, including immune system cells.


HTLV-I and HTLV-II, like all retroviruses, are single-stranded RNA that divide through DNA made possible by the presence of an enzyme, reverse transcriptase, which converts a single-stranded viral RNA into a double-stranded DNA. HTLV-I attacks T lymphocytes; it appears to be the causative agent of certain T- cell leukemias, T-cell lymphomas, and HTLV-I-associated neurologic disease.

Human immunodeficiency virus type 1 (HIV-1)

HIV-1 and HIV-2 are retroviruses that cause the immune destruction of HIV disease and AIDS. HIV-1 is classified as a lentivirus in a subgroup of retroviruses. Retroviruses are single-stranded RNA that convert themselves into DNA through the action of an enzyme, reverse transcriptase. HIV inserts its DNA product into the host cell's DNA, preventing the host cell from carrying out its natural functions and turning it into an HIV factory.

See Lentivirus; Retrovirus.

Human immunodeficiency virus type 2 (HIV-2)

A virus closely related to HIV-1 that has also been found to cause AIDS. It was first isolated in West Africa. HIV-1 and HIV-2 differ in their geographic patterns of infection. HIV-1 remains the most common cause of AIDS and represents the major type distributed worldwide.

Human papillomavirus (HPV)

HPV is transmitted through sexual contact and is the virus that causes genital warts and plays a causative role in cervical dysplasia and cervical cancer.

Humoral immunity

The branch of the immune system that relies primarily on antibodies.

See Cell-mediated immunity (CMI).


An abnormally high concentration of glucose (sugar) in the circulating blood, seen especially in patients with diabetes mellitus.


An increase in the blood levels of triglycerides and cholesterol (fats) that can lead to heart disease and inflammation of the pancreas.


Abnormal increase in the parts of tissue or cells.


Elevated levels of triglycerides (fatty acid compounds) in the bloodstream. High levels contribute to heart disease.


An assumption as a basis for reasoning or argument, or as a guide to experimental investigation.


Reduction of oxygen supply to tissues.