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Glossary of HIV/AIDS Terms

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HAART
See Highly Active Antiretroviral Therapy (HAART) .

Haematocrit
A laboratory measurement that determines the percentage of packed red blood cells in a given volume of blood. In women, red blood cells are normally 37-47% of their blood; in men, red blood cells are normally 40-54% of their blood.

Haematotoxic
Poisonous to the blood or bone marrow.

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

Haemolysis
The rupture of red blood cells.

Hairy Leukoplakia
See Oral Hairy Leukoplakia (OHL) .

Harm Reduction
A prevention activity that aims to provide services to HIV-infected persons 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 seeks to help partners gain earlier access to individualised counselling, HIV testing, medical evaluation, treatment, and other prevention and support services.

HCW
Health care worker

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 abnormal for other temporary reasons.

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

Hepatic
Pertaining to the liver.

Hepatitis
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
Hepatitis B virus (HBV) can cause chronic liver disease, cirrhosis, and hepatocellular carcinoma. Tuberculosis (TB) infection with the bacteria Mycobacterium tuberculosis .

Hepatitis C
Approximately 40% of patients infected with HIV are also infected with the hepatitis C virus (HCV), mainly because the two viruses share routes of transmission. HCV is one of most important causes of chronic liver disease in the United States. Clinical studies have demonstrated that HIV infection causes a more rapid progression of chronic hepatitis C to liver failure in HIV-infected persons.

Hepatomegaly
Enlargement of the liver.

Hepatosplenomegaly
Abnormal enlargement of both the liver and the spleen.

Hepatotoxicity
Liver damage owing 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 or other serious complications. HSV-2 is a precursor of cervical cancer.

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)
The name given to treatment regimens recommended by HIV experts to aggressively decrease viral multiplication and progress of HIV disease. The usual HAART treatment combines three or more 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.

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.

Histoplasmosis
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
Human Immunodeficiency Virus See Human Immunodeficiency Virus Type 1 (HIV-1) ; Human Immunodeficiency Virus Type 2 (HIV-2) .

HIV-1
See Human Immunodeficiency Virus Type 1 (HIV-1) .

HIV-2
See Human Immunodeficiency Virus Type 2 (HIV-2) .

HIV-Associated Dementia
See AIDS Dementia Complex (ADC) .

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

HIV Prevention Counselling
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 (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 where the level of virus stabilises and remains at a particular level in each individual after the period of primary infection.

HIV Viral Load
See Viral Load Test .

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

Home Sample Collection Test
A test kit that a consumer purchases and uses to collect blood (or other bodily fluid) to send away for testing.

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

Hormone
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.

HPV
See Human Papillomavirus (HPV) .

HTLV-1; HTLV-2
HTLV-I and HTLV-II, like all retroviruses, are single-stranded RNA that divide through DNA made possible by the presence of a 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)
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. Also, the genetic material of a retrovirus such as HIV is the RNA itself. HIV inserts its own RNA 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. Although HIV-1 and HIV-2 are similar in how they are transmitted and result in similar opportunistic infections, they have differed 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) .

Hypercholesterolaemia
Abnormally high levels of cholesterol in the bloodstream. High cholesterol levels contribute to heart disease.

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

Hyperglycaemia
An abnormally high concentration of glucose (sugar) in the circulating blood, seen especially in patients with diabetes mellitus. Hyperglycaemia, new onset diabetes mellitus, diabetic ketoacidosis, and worsening of existing diabetes mellitus in patients receiving protease inhibitors have been reported.

Hyperlipidaemia
An increase in the blood levels of triglycerides and cholesterol (fats) that can lead to heart disease and inflammation of the pancreas. As related to HIV, hyperlipidaemia is a side effect of HAART. (All protease inhibitors have been shown to cause hyperlipidaemia in clinical studies.)

Hyperplasia
Abnormal increase in the parts of tissue or cells.

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

Hypogammaglobulinaemia
Abnormally low levels of immunoglobulins. See Antibody .

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

Hypoxia
Reduction of oxygen supply to tissues.

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