V
Also known as: Immunization
Giving a vaccine to stimulate a person's immune response. Vaccination can be intended either to prevent a disease (a preventive vaccine) or to treat a disease (a therapeutic vaccine).
See Related Term(s): Vaccine
Also known as: Inoculation
A substance administered to trigger an immune response against a particular disease. Most vaccines are designed to prevent a person from ever having a particular disease or to only have a mild case of the disease. However, therapeutic vaccines are intended to treat specific diseases. Although researchers are testing vaccines both to prevent and treat HIV/AIDS, no HIV vaccine is currently approved for use outside of clinical trials.
See Related Term(s): Preventive HIV Vaccine, Therapeutic HIV Vaccine
The pox-type virus used in the vaccine that eradicated smallpox. Researchers are studying the possibility of using a modified, milder version of the vaccinia virus to develop a vaccine against HIV infection.
See Related Term(s): Vaccine
A neurological disorder associated with advanced HIV infection. Vacuolar myelopathy causes the protective myelin sheath to pull away from nerve cells of the spinal cord, forming small holes (vacuoles) in nerve fibers. Symptoms of vacuolar myelopathy include weak and stiff legs and unsteadiness when walking.
See Related Term(s): Myelin
In genetically engineered vaccines, a vector is a bacterium or virus that transports antigen-coding genes into the body to provoke an immune response. (The vector itself does not provoke an immune response or cause disease.) A vector may also refer to an organism, especially an insect, that transmits disease-causing agents.
See Related Term(s): Genetic Engineering
Vertical transmission of HIV refers to HIV transmission from an HIV-infected mother to her child during pregnancy, labor and delivery, or breastfeeding (through breast milk).
See Related Term(s): Sexual Transmission
The change in the genetic makeup of a virus population as the viruses mutate and multiply over time. HIV evolves rapidly because of its high mutation and replication rates. Antiretroviral therapy (ART) and the body's immune response can also influence HIV evolution.
When a virus is present in the body but exists in a resting (latent) state without producing more virus. A latent viral infection usually does not cause any noticeable symptoms and can last a long period of time before becoming active and causing symptoms. HIV is capable of viral latency, as seen in the reservoirs of latent HIV-infected cells that persist in a person’s body despite antiretroviral therapy (ART).
See Related Term(s): Latent HIV Reservoir
The amount of HIV in a sample of blood. Viral load (VL) is reported as the number of HIV RNA copies per milliliter of blood. An important goal of antiretroviral therapy (ART) is to suppress a person’s VL to an undetectable level—a level too low for the virus to be detected by a VL test.
See Related Term(s): Viral Load Test
A laboratory test that measures the amount of HIV in a blood sample. Results are reported as the number of copies of HIV RNA per milliliter of blood. Examples of viral load tests include quantitative branched DNA (bDNA), reverse transcriptase-polymerase chain reaction (RT-PCR), and qualitative transcription-mediated amplification. Viral load tests are used to diagnose acute HIV infection, guide treatment choices, and monitor response to antiretroviral therapy (ART).
See Related Term(s): Qualitative Transcription-Mediated Amplification, Quantitative Branched DNA, Reverse Transcriptase-Polymerase Chain Reaction
Also known as: Rebound
When a person on antiretroviral therapy (ART) has persistent, detectable levels of HIV in the blood after a period of undetectable levels. Causes of viral rebound can include drug resistance or poor adherence to an HIV treatment regimen.
See Related Term(s): Undetectable Viral Load
Also known as: Virologic Control
When antiretroviral therapy (ART) reduces a person’s viral load (HIV RNA) to an undetectable level. Viral suppression does not mean a person is cured; HIV still remains in the body. If ART is discontinued, the person’s viral load will likely return to a detectable level.
See Related Term(s): Undetectable Viral Load
Also known as: Tropism
When HIV selectively attaches to a particular coreceptor on the surface of the host cell. HIV can attach to either the CCR5 coreceptor (R5-tropic) or the CXCR4 coreceptor (X4-tropic) or both (dual-tropic).
See Related Term(s): Dual-Tropic Virus, R5-Tropic Virus, X4-Tropic Virus
The presence of viruses in the blood.
Also known as: Virucide
A substance that can destroy or inactivate a virus.
A type of HIV treatment failure. Virologic failure occurs when antiretroviral therapy (ART) fails to suppress and sustain a person’s viral load to less than 200 copies/mL. Factors that can contribute to virologic failure include drug resistance, drug toxicity, and poor treatment adherence.
See Related Term(s): Treatment Failure
The study of viruses and viral diseases.
A microscopic infectious agent that requires a living host cell in order to replicate. Viruses often cause disease in humans, including measles, mumps, rubella, polio, influenza, and the common cold. HIV is the virus that causes AIDS.
Visceral Adipose Tissue (VAT) 
(En español)
Also known as: Intra-Abdominal Fat, Visceral Fat
Fat tissue located deep in the abdomen and around internal organs. Use of certain antiretroviral (ARV) drugs can cause excessive accumulation of visceral adipose tissue (VAT), which increases the risk of heart attack, stroke, and diabetes.
See Related Term(s): Lipodystrophy