H
The time it takes a drug to lose half its original concentration or activity after being introduced into the body. Drug half-life is considered when determining drug dosing.
Health Resources and Services Administration (HRSA) 
(En español)
The primary federal agency for improving access to health care services for people who are uninsured, isolated, or medically vulnerable. Through its HIV/AIDS bureau, the Health Resources and Services Administration (HRSA) administers the Ryan White HIV/AIDS Program, the largest federal program focused exclusively on HIV/AIDS care.
See Related Term(s): Ryan White HIV/AIDS Program
A rare but life-threatening complication of pregnancy that is characterized by
Hemolysis (breakdown of red blood cells),
Elevated
Liver enzyme levels, and a
Low
Platelet count. HELLP develops late in pregnancy, or sometimes after birth.
A laboratory test that measures the volume of red blood cells in whole blood. Hematocrit is normally ordered as part of a complete blood count.
See Related Term(s): Complete Blood Count
Poisonous to the blood and to the organs and tissues involved in the production of blood, such as the bone marrow.
Blood in the urine. The use of certain antiretroviral (ARV) drugs may cause hematuria.
A protein in red blood cells that carries oxygen from the lungs to the tissues of the body. Hemoglobin also refers to the hemoglobin test, which is normally ordered as part of a complete blood count.
See Related Term(s): Complete Blood Count
Destruction of red blood cells. Hemolysis occurs as part of the natural life cycle of red blood cells, or it may be caused by certain conditions or drugs.
See Related Term(s): Red Blood Cell
An inherited blood clotting disorder that most often affects males. The main symptom of hemophilia is prolonged bleeding either spontaneously or after an injury or accident.
Excessive or uncontrollable bleeding from one or more blood vessels. A hemorrhage, which may be internal or external, is often caused by injury or surgical complications or from advanced disease. The use of certain antiretroviral (ARV) drugs may cause internal hemorrhage.
Pertaining to the liver.
See Related Term(s): Liver
Death of liver cells. Hepatic necrosis may be caused by certain antiretroviral (ARV) drugs.
See Related Term(s): Liver
Also known as: Fatty Liver
Excessive accumulation of triglycerides and other fats in liver cells. Use of certain antiretroviral (ARV) drugs may cause hepatic steatosis.
See Related Term(s): Liver
Inflammation of the liver, usually from a viral infection. The most common hepatitis infections are hepatitis A, hepatitis B, and hepatitis C. Hepatitis may also be due to autoimmune disease, alcohol, medications, or toxic agents. Symptoms of hepatitis, if any, can include loss of appetite, nausea and vomiting, and jaundice. Hepatitis can lead to liver damage, liver failure, or cancer. Hepatitis is also often used to refer to the group of viral infections that affect the liver (hepatitis A, B, C, D, and E).
See Related Term(s): Hepatitis B Virus (HBV) Infection, Hepatitis C Virus (HCV) Infection, Jaundice, Liver
Hepatitis B Virus (HBV) Infection (En español)
Infection with the hepatitis B virus (HBV). HBV can be transmitted through blood, semen, or other body fluids during sex or injection-drug use. Because HIV and HBV share the same modes of transmission, people infected with HIV are often also coinfected with HBV. HBV infection progresses more rapidly in people coinfected with HIV than in people infected with HBV alone.
See Related Term(s): Hepatitis, Opportunistic Infection
Hepatitis C Virus (HCV) Infection (En español)
Infection with the hepatitis C virus (HCV). HCV is usually transmitted through blood and rarely through other body fluids, such as semen. HCV infection progresses more rapidly in people coinfected with HIV than in people infected with HCV alone.
See Related Term(s): Hepatitis
Abnormal enlargement of the liver.
See Related Term(s): Liver
Toxic damage to the liver. Drugs, including antiretroviral (ARV) drugs, can cause hepatotoxicity.
See Related Term(s): Liver
Herpes Simplex Virus 1 (HSV-1) Infection (En español)
An infection caused by herpes simplex virus 1 (HSV-1) and usually associated with lesions on the lips, mouth, and face. HSV-1 is very contagious and is transmitted by direct contact with someone who is infected (even if lesions are not visible). Treatment cannot completely clear HSV-1 from the body, but antiviral therapy can shorten and prevent outbreaks and reduce the risk of transmission. People with weakened immune systems, such as people with HIV, are more likely to have lesions that spread to other parts of the body than people with healthy immune systems.
See Related Term(s): Herpesviruses, Opportunistic Infection
Herpes Simplex Virus 2 (HSV-2) Infection (En español)
An infection caused by herpes simplex virus 2 (HSV-2) and usually associated with lesions in the genital or anal area. HSV-2 is very contagious and is transmitted by sexual contact with someone who is infected (even if lesions are not visible). Treatment cannot eradicate HSV-2 from the body, but antiviral therapy can shorten and prevent outbreaks and reduce the risk of transmission. People with weakened immune systems, such as people with HIV, are more likely to have lesions that spread to other parts of the body than people with healthy immune systems.
See Related Term(s): Herpesviruses, Opportunistic Infection
Also known as: Human Herpesviruses
A group of viruses that use DNA as their genetic material. Herpesviruses include herpes simplex viruses 1 and 2 (HSV-1 and -2), varicella zoster virus (VZV or HHV-3), Epstein-Barr virus (EBV or HHV-4), cytomegalovirus (CMV or HHV-5), herpes simplex viruses 6 and 7 (HSV-6 and -7), and Kaposi sarcoma herpesvirus (KSHV or HHV-8).
A lung infection caused by the fungus
Histoplasma capsulatum. Symptoms include fever, chest pain, and dry cough. In people with weakened immune systems, such as people with HIV, histoplasmosis may spread to other parts of the body, including the brain or gastrointestinal tract. Histoplasmosis (disseminated or extrapulmonary) is an AIDS-defining condition in people with HIV.
See Related Term(s): AIDS-Defining Condition, Opportunistic Infection
HIV Prevention Trials Network (HPTN) (En español)
A federally funded, worldwide clinical trials network that develops and tests the safety and efficacy of primarily non-vaccine interventions designed to prevent the transmission of HIV.
See Related Term(s): Clinical Trial
HIV Vaccine Trials Network (HVTN) (En español)
A federally funded international clinical trials network that works towards finding an effective and safe HIV vaccine. HIV Vaccine Trials Network (HVTN) conducts clinical trials on preventive HIV vaccines and educates community members on the general science of HIV/AIDS vaccines and associated research methods.
See Related Term(s): Clinical Trial, Preventive HIV Vaccine
HIV Viral Core
Also Known As: Core
HIV Viral Envelope
Also Known As: Envelope
One of the two types of HIV, the virus that causes AIDS. AIDS is the most advanced stage of HIV infection. HIV-1 is transmitted through direct contact with HIV-infected body fluids, such as blood, semen, and genital secretions, or from an HIV-infected mother to her child during pregnancy, delivery, or breastfeeding (through breast milk). HIV-1 is responsible for the majority of HIV infections worldwide. In the United States, unless otherwise noted, the term “HIV” primarily refers to HIV-1.
See Related Term(s): Acquired Immunodeficiency Syndrome, HIV-2
One of the two types of HIV, the virus that causes AIDS. AIDS is the most advanced stage of HIV infection. HIV-2 infection is endemic to West Africa. Like HIV-1, HIV-2 is transmitted through direct contact with HIV-infected body fluids, such as blood, semen, and genital secretions, or from an HIV-infected mother to her child during pregnancy, delivery, or breastfeeding (through breast milk). HIV-2 infection generally takes longer to progress to symptomatic HIV/AIDS and has a lower mortality rate than HIV-1 infection.
See Related Term(s): Acquired Immunodeficiency Syndrome, HIV-1
HIV-Associated Nephropathy (HIVAN) (En español)
Kidney disease associated with HIV infection. HIV-associated nephropathy (HIVAN) usually begins with large amounts of protein in the urine (proteinuria) and progresses rapidly to total kidney failure. HIVAN is very uncommon in people whose HIV is effectively controlled by antiretroviral (ARV) drugs.
See Related Term(s): Kidneys
HIV-Associated Neurocognitive Disorders (HAND) (En español)
A range of increasingly severe central nervous system complications associated with HIV infection. HIV-associated neurocognitive disorders (HAND) range from mild problems with memory, language, and reasoning to the more severe HIV-associated dementia (HAD).
See Related Term(s): HIV-Associated Dementia
Also known as: HLA-B*5701 Testing
A test that detects the presence of HLA-B*5701. The HLA-B*5701 molecule is linked to hypersensitivity to the antiretroviral (ARV) drug abacavir. A person who tests positive for HLA-B*5701 should not use abacavir.
See Related Term(s): Human Leukocyte Antigen
HMG-CoA Reductase Inhibitor
Also Known As: Statin
Also known as: Hodgkin Disease
A type of lymphoma (cancer of the lymphatic system). Hodgkin lymphoma is characterized by progressive enlargement of the lymph nodes, spleen, and general lymphoid tissue and by the presence of large, usually multinucleate cells of unknown origin called Reed-Sternberg cells. In people with HIV, Hodgkin lymphoma is an AIDS-related cancer.
See Related Term(s): AIDS-Related Cancer, Lymphoma
Transmission of HIV, or other infectious disease, from one person to another, except from parent to child (vertical transmission). Horizontal transmission of HIV can occur during sex or needle sharing as the result of contact with the semen, vaginal fluid, or blood of an HIV-infected partner.
See Related Term(s): Sexual Transmission, Vertical Transmission
A chemical messenger produced by the body and carried by the blood to tissues and organs. Hormones regulate many different body processes, including growth and development, metabolism, sexual function, reproduction, and mood. HIV can affect the production of hormones, such as estrogen and testosterone.
The animal or plant (or specific part of an animal or plant) in which another organism or microorganism lives. For example, CD4 cells infected with HIV are called host cells.
Human Growth Hormone (hGH) (En español)
A hormone that is produced by the pituitary gland and stimulates the growth of bones, muscles, and other organs. A synthetic version of human growth hormone (hGH) is approved by the Food and Drug Administration (FDA) for the treatment of AIDS-related wasting syndrome.
See Related Term(s): Wasting Syndrome
Human Herpesvirus 6 (HHV-6) Infection (En español)
An infection caused by human herpesvirus 6 (HHV-6). HHV-6 is primarily transmitted through saliva and usually causes disease only in children or people with weakened immune systems. HHV-6 can cause neurological diseases, such as encephalitis and febrile seizures. HHV-6 can also cause fever and rash (roseola), which mostly affects children between 6 months and 2 years old.
See Related Term(s): Herpesviruses, Opportunistic Infection
Human Herpesvirus 7 (HHV-7) (En español)
A type of herpesvirus found in saliva of people infected with human herpesvirus 7 (HHV-7). HHV-7 has not been definitively documented to cause a specific disease.
See Related Term(s): Herpesviruses
Human Immunodeficiency Virus (HIV) (En español)
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 HIV-infected body fluids, such as blood, semen, and genital secretions, or from an HIV-infected mother to her child during pregnancy, birth, or breastfeeding (through breast milk).
See Related Term(s): Acquired Immunodeficiency Syndrome, HIV-1, HIV-2, Retrovirus
Human Leukocyte Antigen (HLA) (En español)
A group of molecules found on the surface of almost every cell in the body. Human leukocyte antigens (HLAs) present protein fragments (peptides) to immune cells. If the cells recognize the peptides as foreign, the body mounts an immune response. Some diseases and drug reactions are linked to certain types of HLAs.
See Related Term(s): Major Histocompatibility Complex
Human T-Cell Lymphotropic Virus Type I (HTLV-I) (En español)
A retrovirus that infects only T lymphocytes (T cells). Human T cell lymphotropic virus type 1 (HTLV-1) is transmitted through exposure to contaminated blood, through sexual contact, and from an infected mother to her child at birth or through breastfeeding via breast milk. HTLV-1 is prevalent mostly in Japan, Africa, the Caribbean Islands, and South America. HTLV-1 can cause adult T-cell leukemia/lymphoma, a rare and aggressive cancer of the white blood cells.
See Related Term(s): Retrovirus
A higher-than-normal level of gamma globulin in the blood. Gamma globulins are a group of blood proteins that include most antibodies. Hypergammaglobulinemia may occur with chronic infections, including HIV infection.
Abnormally high blood sugar (glucose) level. Use of some antiretroviral (ARV) drugs may cause hyperglycemia.
Excess lipids (cholesterol, triglycerides, or both) in the blood. Hyperlipidemia increases the risk of high blood pressure, heart disease, and stroke. Hyperlipidemia may be caused by HIV infection or use of some antiretroviral (ARV) drugs.
An increase in the number of cells in a tissue or organ. Hyperplasia may be due to a normal, increased demand for cells or may be a sign of precancerous changes.
Also known as: Hypersensitivity Reaction
An exaggerated immune response to a specific antigen or drug. Hypersensitivity reactions, including allergic reactions, can be life-threatening. Use of some antiretroviral (ARV) drugs may cause a hypersensitivity reaction.
Also known as: High Blood Pressure
Persistently elevated blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries. Hypertension can harm the arteries and increase the risk of stroke, heart attack, and kidney failure. Use of some antiretroviral (ARV) drugs may cause hypertension.
Excessive accumulation of triglycerides (a type of fat) in the blood. Hypertriglyceridemia increases the risk of high blood pressure, heart disease, and stroke. Use of some antiretroviral (ARV) drugs can cause hypertriglyceridemia.
Much higher-than-normal levels of uric acid in the blood. Hyperuricemia may be an adverse effect of some antiretroviral (ARV) drugs.
Abnormally low levels of gamma globulin in the blood. Gamma globulins are a group of blood proteins that include most antibodies. People with hypogammaglobulinemia are at high risk for infections. Hypogammaglobulinemia may be due to certain genetic diseases or to acquired diseases such as HIV.
Condition in which the sex glands produce little or no hormones. Hypogonadism commonly occurs during HIV infection.
See Related Term(s): Hormone
An insufficient supply of oxygen to the cells and tissues of the body.