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HIV Glossary Plain-language definitions

HIV Glossary

Last reviewed:

Health information — Educational information, not medical advice. Talk with your healthcare provider about your care and treatment decisions.

Understanding the language helps you navigate your care with confidence. Every definition is written for people living with HIV, newly diagnosed people, caregivers, and advocates — in plain, person-first language.

Last reviewed:

Sourced from CDC, NIH, HIV.gov, HRSA.

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340B Drug Pricing Program (340B)
A federal program created in 1992 that lets clinics and hospitals serving people with low incomes and people who are uninsured buy outpatient medicines at discounted prices. Drug makers that take part in Medicaid must sell covered drugs to these "covered entities" at or below a set ceiling price. HRSA runs the program, and savings often fund HIV services. [1]

A

ACA (Affordable Care Act) HIV Provisions (ACA; Obamacare)
The health care law that made coverage easier to get and keep for people living with or at risk for HIV. Insurers cannot deny or drop coverage because of a pre-existing condition like HIV; Medicaid expanded in participating states; and Marketplace plans, tax credits, and required preventive services make testing, prevention, and HIV care more affordable. [2]
Acute HIV Infection (Primary HIV infection; Stage 1 HIV)
The early phase after HIV is acquired, before antibodies are reliably detectable. Symptoms may occur around 2–4 weeks after acquisition, but timing varies. Viral load can be high, and an RNA test can detect infection before an antibody test. Symptoms alone cannot diagnose HIV. [3]
ADAP (AIDS Drug Assistance Program)
The AIDS Drug Assistance Program is a federally funded program that provides HIV medications and other HIV-related services to people with HIV who have low incomes or who are uninsured or underinsured. ADAP services are available in all 50 states and the U.S. territories, and each state runs its own program with its own enrollment rules. [4]
Adherence
Taking medicine as prescribed, including its dose, timing and food instructions. Adherence helps an effective ART regimen maintain viral suppression. Maintaining a viral load below 200 copies/mL on ART prevents sexual HIV transmission; taking pills alone is not proof of suppression. [5]
AIDS (Acquired Immunodeficiency Syndrome; Stage 3 HIV)
The most advanced stage of HIV disease. In adults and adolescents it can be diagnosed by an AIDS-defining condition or a CD4 count below 200 cells/mm³. It is not limited to people who have never received treatment. Effective ART can support immune recovery, although outcomes vary. [6]
Antibody (Immunoglobulin)
A protein your immune system makes in response to something it recognizes as foreign, such as a virus. Antibodies attach to that target and help destroy it. Many HIV tests work by looking for HIV antibodies in blood or oral fluid rather than looking for the virus itself. [7]
Antigen/Antibody Test (Ag/Ab combination test; combo test)
A test that looks for two things at once: HIV antibodies and HIV-1 p24 antigen, a protein from the virus's core. Because it catches the antigen first, it finds HIV earlier than antibody-only tests — usually 18 to 45 days after exposure with a blood draw. This is the standard lab screening test in the U.S. [8]
Antiretroviral Therapy (ART) (HIV treatment; combination therapy; HAART)
Treatment with a combination of antiretroviral medicines to suppress HIV. Many regimens use three drugs, while selected people can use a two-drug regimen or a complete long-acting injectable regimen. ART is recommended for everyone with HIV, with prompt clinical assessment and initiation as soon as appropriate. [9]
Apretude (cabotegravir extended-release injectable (CAB-LA for PrEP))
Long-acting cabotegravir for PrEP, FDA-approved in 2021 for eligible adults and adolescents weighing at least 35 kg to prevent sexually acquired HIV. The first two injections are one month apart, followed by injections every two months. HIV testing and scheduled follow-up remain essential. [10]

B

Baseline Testing (Baseline labs)
The initial clinical and laboratory assessment after an HIV diagnosis, including viral load, CD4 count, resistance testing and tests for other conditions. It guides care and treatment selection. ART often starts before all results return, with adjustment when needed. [11]
Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF))
A single-tablet HIV treatment that combines three medicines — bictegravir, emtricitabine, and tenofovir alafenamide — in one pill taken once a day. The FDA approved it on February 7, 2018. Combination pills like this lower the number of pills a person takes daily, which can make treatment simpler to stay on. [12]

C

Cabenuva (cabotegravir/rilpivirine (CAB/RPV))
Cabotegravir plus rilpivirine injections, a complete long-acting ART regimen given monthly or every two months. Its approved use replaces a stable regimen in eligible virally suppressed adults and adolescents aged at least 12 years and weighing at least 35 kg, without prior treatment failure or relevant resistance. A clinician assesses suitability. [13]
Capsid Inhibitor (Lenacapavir; Sunlenca; Yeztugo)
A drug class that interferes with HIV’s capsid, the protein shell around its genetic material. Lenacapavir has different products and indications: Sunlenca is used with other ART for specified heavily treatment-experienced adults; Yeztugo is PrEP for eligible people without HIV. These products are not interchangeable regimens. [14]
CCR5 Antagonist (CCR5 inhibitor)
A class of HIV medicines that covers the CCR5 coreceptor — a doorway on the surface of some immune cells, including CD4 cells — so HIV cannot use it to get in. A test can show whether a person's HIV uses that particular doorway before this medicine is prescribed. [15]
CD4 Count (CD4 cell count; T-cell count)
The number of CD4 T cells in a blood sample, an important measure of immune function and risk from opportunistic infections. Viral load is the main measure of whether ART is suppressing HIV; CD4 recovery and viral suppression are related but different outcomes. [16]
CD4 Percentage (CD4 cell percentage)
The share of your lymphocytes (a type of white blood cell) that are CD4 cells. In some situations — for example, in children with HIV under 5 years old — the CD4 percentage gives a clearer picture than the CD4 count of immune health and how well treatment is working. [17]
Clinical Trial (Interventional study)
A research study that tests whether a new medicine or other approach is safe and works well in people. Volunteers join clinical trials to help find better ways to prevent, diagnose, treat, and understand illness. Trials run in phases, and people living with HIV have shaped nearly every advance in HIV care by taking part. [18]
Coinfection
Having two or more infections at the same time. For example, a person living with HIV may also be living with hepatitis C, tuberculosis, or both. Coinfections are common, treatable, and worth screening for, because treating them together protects your health. [19]
Comorbidity (Comorbid condition)
Having two or more health conditions at the same time — for example, living with HIV along with high blood pressure or diabetes. Because HIV treatment now supports long lives, much of HIV care today focuses on managing comorbidities alongside HIV. [20]
Condomless Sex
Sex without a condom. It is not necessarily sex without HIV prevention: effective PrEP or maintained viral suppression can prevent sexual HIV transmission. Condoms also help reduce some other STIs and pregnancy; PrEP and U=U do not provide those protections. [21]
Confirmatory Test (Supplemental test; follow-up test)
Additional testing used to resolve a reactive HIV screening result. In the standard U.S. laboratory sequence, an antigen/antibody screen is followed by an HIV-1/HIV-2 antibody differentiation test and, when indicated, an HIV RNA test. A reactive screening or self-test needs follow-up; the exact diagnostic approach depends on the clinical situation. [22]
Criminalization (HIV criminalization)
The use of criminal laws against conduct associated with a person’s HIV status. Laws, penalties and defenses differ by jurisdiction, and some cover conduct with little or no transmission risk. An undetectable viral load is not automatically a legal defense. Check current law rather than relying on an undated state count. [23]

D

Descovy (emtricitabine/tenofovir alafenamide (FTC/TAF))
Emtricitabine plus tenofovir alafenamide (F/TAF), a two-drug pill used with other HIV medicines for treatment. It can also be used as PrEP for eligible people, but is not indicated for HIV prevention through receptive vaginal sex. It is not a complete HIV treatment regimen by itself. [24]
Diagnosed vs Undiagnosed HIV (Knowledge of status)
Not everyone living with HIV knows it yet. "Knowledge of status" is the share of people with HIV who have been tested and diagnosed, calculated by dividing people living with diagnosed HIV by total estimated HIV prevalence, diagnosed and undiagnosed. The EHE goal is 95 percent, up from 85.8 percent in 2017. [25]
Disclosure
Sharing your HIV status with someone. Decisions about friends, family and coworkers can be personal, while legal obligations concerning sexual activity vary by jurisdiction. Partner services can help with confidential notification, but confidentiality is not a guarantee that a partner cannot infer who prompted it. [26]
Dovato (dolutegravir/lamivudine (DTG/3TC))
A single-tablet, two-drug HIV treatment combining dolutegravir and lamivudine, FDA-approved on April 8, 2019. Federal guidelines recommend this two-drug combination as a first regimen for many people, with a few exceptions your care team checks for first. [27]
DoxyPEP (Doxycycline post-exposure prophylaxis)
Prescribed doxycycline taken after sex to help prevent some bacterial STIs, not HIV. CDC recommends shared decision-making for MSM and transgender women with a bacterial STI in the past year: 200 mg within 72 hours after sex, no more than 200 mg in 24 hours. Follow-up testing and reassessment are required. [28]
Drug Resistance (Resistance)
Changes in HIV that reduce a drug’s ability to suppress it. Resistance can develop during treatment or be present when HIV is acquired. Resistance tests, treatment history and interaction/adherence review help identify an effective regimen; no test guarantees that every chosen medicine will work. [29]

E

EHE (Ending the HIV Epidemic in the U.S.)
Ending the HIV Epidemic in the U.S. is a federal initiative to sharply reduce new HIV transmissions by scaling up four strategies: diagnose, treat, prevent, and respond. It directs extra resources, expertise, and technology to 57 areas of the country where HIV transmission is most common, with a goal of at least 90 percent fewer new infections by 2030. [30]
EHE Jurisdictions (EHE priority jurisdictions)
The initial EHE priority areas: 48 counties, Washington, D.C., San Juan, Puerto Rico, and seven states with substantial rural HIV diagnoses. The 48 counties, D.C. and San Juan together accounted for more than half of U.S. diagnoses in 2016–2017; the seven states were included to address rural needs. [31]
ELISA (Enzyme-Linked Immunosorbent Assay; enzyme immunoassay)
A lab test that looks for HIV antibodies in blood or oral fluid. The immune system makes these antibodies in response to HIV. A positive ELISA result always needs a second, follow-up test before anyone can be given a definite HIV diagnosis. [32]
Elite Controller (Natural viral controller)
A rare person with HIV who maintains very low or undetectable viral load without ART. Elite control and long-term nonprogression overlap but are not identical: a person can maintain CD4 counts without fully suppressing virus. Natural control can be lost, and NIH recommends ART rather than assuming treatment is unnecessary. [33]
Entry Inhibitor
A group of HIV medicines that stops HIV from getting into a CD4 cell in the first place. The group includes fusion inhibitors, CCR5 antagonists, and post-attachment inhibitors. These are usually used by people whose HIV has become resistant to other classes. [34]
Enzyme Immunoassay (EIA) (EIA; ELISA)
Another name for the ELISA — a lab test that looks for HIV antibodies in blood or oral fluid, made by the immune system in response to HIV. A reactive EIA is a screen, not a diagnosis: a second, different test must confirm it before anyone is told they have HIV. [35]

F

False Negative
A test result that says a condition is not there when it actually is. A false-negative HIV test tells someone they do not have HIV when they do. This is why testing again after the window period matters if there was a possible exposure. [36]
Fourth-Generation Test (4th-generation antigen/antibody immunoassay)
The lab test CDC recommends starting HIV testing with. It detects HIV-1 and HIV-2 antibodies plus HIV-1 p24 antigen, so it can find HIV before antibodies appear — that is, during acute infection. If it is reactive, the lab runs a test that tells HIV-1 and HIV-2 antibodies apart, and sometimes a NAT. [37]
Fusion Inhibitor
A class of HIV medicines that keeps HIV's outer envelope from merging with the membrane of a CD4 cell. Because that merging is how HIV gets inside, blocking it keeps the virus out of the cell. [38]

G

Genotype Test (Genotypic antiretroviral resistance test (GART))
A resistance test that reads HIV's genes to spot mutations that make certain HIV medicines less effective. Results guide your care team in choosing or changing a regimen. A blood sample for genotype testing is usually drawn when you start care — and it should not delay starting treatment. [39]
Getting to Zero (Zero new infections, zero discrimination, zero AIDS-related deaths)
A framing that came out of UNAIDS strategy and is now used by cities and states: zero new HIV infections, zero discrimination, and zero AIDS-related deaths. It pairs treatment and prevention goals with human rights goals — including repealing punitive laws and ending violence and stigma. [40]
Global Fund (The Global Fund to Fight AIDS, Tuberculosis and Malaria)
A worldwide partnership that raises and invests more than US$4 billion a year to fight HIV, tuberculosis, and malaria in more than 100 of the hardest-hit countries. It brings together governments, civil society, communities, health workers, and private partners, and countries themselves decide how best to shape their response. [41]

H

Harm Reduction
A set of practical, respectful strategies for reducing the harms tied to drug use and other risks — without requiring anyone to stop first. Harm reduction accepts a person's own goals, treats them with dignity, and counts any step that reduces harm as progress. Abstinence is one possible goal on that continuum, not the price of entry. [42]
Hepatitis B (HBV) (Hepatitis B virus infection)
A virus that affects the liver and can pass through blood, semen, or other body fluids during sex or through shared injection equipment. In people living with both HBV and HIV, hepatitis B tends to progress faster than in people with HBV alone. There is a vaccine, and treatment choices matter — some HIV medicines also treat HBV. [43]
Hepatitis C (HCV) (Hepatitis C virus infection)
Hepatitis C is a bloodborne viral infection of the liver. Sexual transmission can also occur in some circumstances. HIV coinfection can increase liver-disease risk, and most people can be cured with appropriate direct-acting antivirals. Cure does not provide immunity against reinfection. [44]
HIPAA
The Health Insurance Portability and Accountability Act. Its Privacy Rule applies to specified healthcare providers, health plans, clearinghouses and business associates, not every person or app. It permits certain uses and disclosures without individual authorization, including treatment, payment, healthcare operations and specified public-health reporting. Other laws may provide additional protections. [45]
HIV (Human Immunodeficiency Virus)
The virus that, without treatment, can lead to AIDS. HIV is a retrovirus with two types, HIV-1 and HIV-2. It passes through direct contact with certain body fluids, such as blood, semen, and vaginal fluid, or from a parent to a child during pregnancy, birth, or breastfeeding. Treatment keeps HIV under control. [46]
HIV Drug Resistance Test (Phenotype) (Phenotypic antiretroviral resistance test; phenotypic assay)
A resistance test that grows a person's own HIV against different amounts of HIV medicines to see which ones still hold it back. Unlike a genotype test, which reads the virus's genes, a phenotype test measures behavior directly. It is mainly used when resistance is complicated, to help pick a regimen that will work. [47]
HIV RNA Test (NAT) (Nucleic acid test; NAAT; nucleic acid amplification test)
A nucleic acid test looks for HIV genetic material in blood. Depending on the test, it can help diagnose HIV or measure viral load. CDC lists a usual detection window of 10–33 days after exposure; use of PrEP or PEP and the clinical situation can affect interpretation and follow-up. [48]
HIV Test Positivity Rate (Percent positivity)
A program measure: the share of HIV tests done that came back positive. CDC calculates it by dividing positive test events by all test events. Programs also track newly diagnosed positivity separately. A higher rate can mean testing is reaching the people who most need it. [49]
HIV-1 vs HIV-2 (HIV type 1; HIV type 2)
There are two types of HIV. HIV-1 causes most HIV worldwide, and in the U.S. "HIV" usually means HIV-1. HIV-2 is found mainly in West Africa and generally takes longer to progress. Both pass the same ways, and both are treatable — though some medicines work differently against HIV-2, so knowing the type matters. [50]
Home HIV Test (HIV self-test; self-testing)
An HIV test performed at home or another private location. OraQuick is an FDA-approved oral-fluid antibody self-test; follow its age limits, instructions and result-reading time. A reactive result requires follow-up, and a negative result during the window period may miss recent infection. Do not assume every online self-collection kit is FDA-authorized. [51]
HOPWA (Housing Opportunities for Persons With AIDS)
Housing Opportunities for Persons With AIDS is the only federal program dedicated to the housing needs of people with HIV who have low incomes, and their families. HUD's Office of HIV/AIDS Housing runs it, and grantees work with nonprofits and housing agencies to provide housing plus supportive services. [52]
Housing First
A housing approach that offers permanent housing without requiring sobriety or completion of treatment first. Support services are offered rather than made a prerequisite. It does not mean that all lease obligations disappear or that eviction can never occur; tenancy rules and program availability still matter. [53]
HRSA (Health Resources and Services Administration)
The Health Resources and Services Administration is the main federal agency working to improve access to health care for people who are uninsured, isolated, or hit hardest by health problems. Through its HIV/AIDS Bureau, HRSA runs the Ryan White HIV/AIDS Program, the largest federal program focused only on HIV care. [54]

I

Immune Reconstitution & IRIS (Immune Reconstitution Inflammatory Syndrome (IRIS))
Immune reconstitution means recovery of immune function with effective treatment. Sometimes this recovery triggers an excessive inflammatory response to an existing infection, called IRIS. It can reveal an unrecognized infection or worsen symptoms of one being treated. IRIS ranges from mild to life-threatening and needs clinical assessment. [55]
Incidence (New infections)
The number of new cases of a condition that happen in a certain place over a certain period of time. HIV incidence means new HIV infections — which is different from new diagnoses, since someone can acquire HIV years before they are diagnosed. [56]
Integrase Inhibitor (Integrase strand transfer inhibitor (INSTI))
A class of HIV medicines that blocks integrase, an HIV enzyme. HIV uses integrase to insert its genetic material into the DNA of a CD4 cell; blocking it stops HIV from making copies of itself. Integrase inhibitors anchor most first-line regimens today because they work fast and are usually well tolerated. [57]

K

Kaposi Sarcoma (KS)
A rare cancer of the cells lining lymph and blood vessels. It causes red or purple patches called lesions under the skin or in the mouth, nose, and throat, and sometimes in the digestive tract, liver, or lungs. It mainly affects people with weakened immune systems, and in people with HIV it is an AIDS-defining condition. [58]

L

Late Diagnosis
Diagnosis after HIV has already caused substantial immune damage; definitions used in research and surveillance vary. It is a reason for prompt evaluation and treatment planning. Certain serious opportunistic infections can change the timing of ART, so do not treat immediate dosing as universal for every advanced presentation. [59]
Linkage to Care
The step between an HIV diagnosis and actually getting into medical care. CDC measures it as having at least one CD4 or viral load test within one month of diagnosis — including tests done the same day. Fast linkage means faster treatment, and it is something clinics and navigators are responsible for making easy. [60]
Linkage-to-Care Coordinator (Care navigator; linkage coordinator)
A worker who helps someone connect with HIV care after diagnosis, through referrals, appointments and practical support. Titles, staffing arrangements and available services vary by program; a coordinator cannot guarantee that every barrier or delay will be removed. [61]
Long-Acting Injectable (LAI; long-acting ART)
Medicine given by injection on a schedule that may be monthly, every two months or every six months, depending on the product. HIV treatment and PrEP products have different indications. Some injections form a complete treatment regimen; others must be combined with additional medicines. [62]
Long-Term Survivor (LTS)
A community term for people who have lived with HIV for many years, including people from the era before effective combination ART and people who acquired HIV early in life. It has no single medical duration cutoff. Lifetime survivors have a distinct history within this broader community. Awareness Day is June 5. [63]

M

Medicaid
A public health-insurance program jointly funded by states and the federal government. States administer it under federal rules, with eligibility and benefits that vary. HIV alone does not establish eligibility. Florida has not adopted the ACA adult Medicaid expansion; check current coverage categories and requirements. [64]
Molecular Surveillance (HIV cluster detection)
A public-health method that compares partial genetic sequences of HIV to identify clusters that may indicate rapid transmission and gaps in care. It analyzes the virus, not a person’s genome, and cannot prove that a particular person transmitted HIV to another. Data protection and community engagement are important. [65]
MPT (Multipurpose Prevention Technology)
Multipurpose prevention technologies are products designed to meet more than one sexual and reproductive health need at once. Condoms are an example that already exists. Newer MPTs in development include rings, films, implants, gels, and the Dual Prevention Pill, which combines oral PrEP with birth control in one daily pill. [66]

N

New HIV Diagnoses (HIV diagnoses)
People receiving a new HIV diagnosis during a reporting period, which is different from the number who acquired HIV during that period. CDC’s current surveillance release covers the U.S. and seven territories and freely associated states. Provisional counts can change as reporting becomes more complete. [67]
NNRTI (Non-nucleoside reverse transcriptase inhibitor)
A class of HIV medicines that attaches to reverse transcriptase and blocks it, stopping HIV from copying its genetic material. NNRTIs work on the same enzyme as NRTIs but in a different way, so the two classes are often used together in a regimen. [68]
nPEP (Non-occupational post-exposure prophylaxis)
HIV post-exposure prophylaxis after a nonwork exposure, such as sex or shared injection equipment. It requires urgent assessment and, when indicated, a 28-day medicine course started as soon as possible, ideally within 24 hours and no later than 72 hours. Follow-up testing is needed. [69]
NRTI (Nucleoside reverse transcriptase inhibitor)
A class of HIV medicines that blocks reverse transcriptase, an enzyme HIV needs to turn its RNA into DNA. Without that step, HIV cannot copy itself. NRTIs such as emtricitabine, lamivudine, and tenofovir form the backbone of most HIV regimens. [70]

O

oPEP (Occupational post-exposure prophylaxis)
HIV post-exposure prophylaxis after a workplace exposure, such as a needlestick. Report the exposure promptly for urgent assessment. Hepatitis B has separate vaccine/immune-globulin prevention rules. There is no recommended PEP for hepatitis C; HCV exposure requires testing and follow-up instead. [71]
Opportunistic Infection (OI) (OI)
An infection that shows up more often, or hits harder, in people whose immune systems are weakened — including people with untreated HIV or people on chemotherapy. HIV treatment that restores the immune system is the best protection, and most OIs can be prevented or treated. [72]

P

PEP (Post-exposure prophylaxis)
Medicine used after a possible HIV exposure to reduce the chance of infection. HIV PEP is urgent, normally lasts 28 days and should start as soon as possible, no later than 72 hours after a qualifying exposure. Hepatitis B prevention is different; hepatitis C does not have recommended PEP. [73]
PEPFAR (President's Emergency Plan for AIDS Relief)
The U.S. President’s Emergency Plan for AIDS Relief, launched in 2003 to support the global HIV response. It is a U.S. government program coordinated through the Department of State with implementing partners and country programs. Funding, organizational arrangements and service availability can change. [74]
Person-First Language (Person-centered language)
Language that centers the person rather than a condition or status — "a person living with HIV" rather than "an HIV-infected person." UNAIDS guidance notes that language can carry stigma that affects whether people test, seek care, and stay in treatment. Some communities prefer identity-first language, so asking about local preference matters. [75]
PLHIV (People living with HIV)
An abbreviation for people living with HIV. Person-first wording is widely recommended to avoid reducing people to a diagnosis. Individual preferences differ, and someone may choose “HIV-positive” or another term for themself. Ask and respect that choice. [76]
Pneumocystis Pneumonia (PCP) (PJP; Pneumocystis jirovecii pneumonia)
A lung infection caused by the fungus Pneumocystis jirovecii, with symptoms like a dry cough, fever, and shortness of breath. The fungus is common in the environment and harmless to people with healthy immune systems. In people with HIV, PCP is an AIDS-defining condition, and it can be both prevented and treated. [77]
PrEP (Pre-exposure prophylaxis)
HIV medication for people without HIV to prevent acquisition. Options include daily pills and long-acting injections, with product-specific eligibility, testing and dosing. Descovy is not indicated for receptive vaginal exposure. PrEP does not prevent other STIs or pregnancy; condoms and other tools can address those needs. [78]
PrEP2Prevent (NCT05281393)
An NIH-funded research study testing an online PrEP navigation and activation program for young men who have sex with men and young transgender and nonbinary people. It pairs a mobile health platform with a patient navigator, peer support, and goal setting to help people get on and stay on PrEP. [79]
Prevalence
The number or share of people living with a particular condition in a population at a given time. HIV prevalence counts everyone living with HIV, whether they were diagnosed last month or twenty years ago. [80]
Protease Inhibitor (PI) (PI)
A class of HIV medicines that blocks protease, an HIV enzyme. Without protease, newly made HIV stays immature and cannot go on to infect other CD4 cells. PIs are dependable options, often used when resistance or other health factors rule out other classes. [81]
Provirus (Proviral DNA)
HIV DNA that has been integrated into a host cell’s DNA. HIV first reverse-transcribes its RNA into DNA, then integrates it; unintegrated viral DNA is not yet a provirus. Cells carrying integrated HIV can persist during effective ART, contributing to the difficulty of curing HIV. [82]

R

Rapid HIV Test (Point-of-care test)
An HIV screening test that gives results in under 30 minutes, using blood from a finger stick or oral fluid. Most rapid tests look for HIV antibodies, and a rapid antigen/antibody version also exists. A positive rapid result is preliminary: it always needs a follow-up test to confirm a diagnosis. [83]
Rapid Start (Rapid ART initiation; same-day start)
Starting ART on the day of diagnosis or soon afterward. NIH recommends prompt initiation with clinical assessment, medication review and support. Certain serious opportunistic infections may require a clinician-directed delay; rapid start is a care approach, not a reason to skip evaluation. [84]
Recency Testing (Recency assay; RITA)
A surveillance tool that uses lab markers to estimate whether someone acquired HIV recently — usually within about the past year — or longer ago. Results are combined with viral load and other information in a recent infection testing algorithm. WHO and UNAIDS say these results are for public health planning, not for individual care, and are not given back to individuals. [85]
Reservoir (Latent HIV reservoir)
Resting CD4 cells and other cells that carry HIV but are not actively making new virus. These latent reservoirs form in the earliest days of HIV and survive even when treatment drives the viral load to undetectable. Because ART cannot clear them, it cannot cure HIV — and shrinking them is a major focus of cure research. [86]
Retention in Care
Staying connected to HIV care over time. CDC measures it as having at least two CD4 or viral load tests, at least three months apart, during a year. Life gets in the way for everyone, and clinics, case managers, and peer navigators exist to help you get back in care whenever you need to. [87]
Ryan White Parts A/B/C/D/F (RWHAP Parts)
The Ryan White program has five parts, each funding something different. Part A funds care in the cities and counties most affected by HIV. Part B funds states and territories, including ADAP. Part C funds outpatient care at community clinics. Part D funds care for women, infants, children, and youth. Part F funds provider training, innovation, dental care, and the Minority AIDS Initiative. [88]
Ryan White Program (Ryan White HIV/AIDS Program (RWHAP); CARE Act)
A federal program administered by HRSA that supports HIV care, medicines and related services for eligible people with low incomes. It serves more than half of people with diagnosed HIV in the U.S. It is not insurance, and local income rules, covered services and other coverage affect eligibility and payment. [89]

S

Same-Day Start (Same-day ART initiation)
Beginning ART on the day of diagnosis when clinically appropriate and feasible. It can shorten time to suppression and improve engagement in care. Clinics must still assess symptoms, other infections, medication suitability and access; not every patient or clinic follows one identical starter-pack process. [90]
Sero-prevalence (Seroprevalence)
How common a condition is in a defined group of people at one point in time, measured through blood tests. For HIV, seroprevalence surveys estimate what share of a population has HIV antibodies. Public health programs use these estimates to understand where HIV is concentrated and where testing, prevention, and care should be strengthened. [91]
Seroconversion
The point when the body has made enough HIV antibodies for an antibody test to detect them, usually within a few weeks of acquiring HIV. At seroconversion, an HIV antibody test result changes from negative to positive. [92]
Serodifferent (Mixed-status couple; serodiscordant)
A couple in which one partner is living with HIV and the other is not. Also called a mixed-status couple. When the partner living with HIV is on treatment with an undetectable viral load, HIV is not passed through sex — and the other partner may also choose PrEP. [93]
Serosorting
Choosing sex partners who have the same HIV status you do, or saving condomless sex for partners of the same status. It has real limits as a strategy: an HIV-negative person only knows their status as of their last test, so serosorting is often combined with — or replaced by — PrEP and treatment. [94]
Sexual Health Clinic (STI clinic; STD clinic)
A clinic that specializes in sexual health care — timely, confidential, and culturally sensitive. Services usually include STI and HIV testing and treatment, PrEP and nPEP, vaccinations, condoms, counseling, and partner services. Many offer walk-in, low-cost care and act as a safety net for people without insurance. [95]
Single-Tablet Regimen (STR) (STR; fixed-dose combination (FDC))
A complete HIV treatment regimen in one tablet, usually taken once daily. This is different from any fixed-dose combination: a combination pill can contain multiple medicines yet still need another drug to make a complete regimen. Your prescriber determines the full treatment plan. [96]
Stigma (HIV-related stigma)
Negative beliefs and attitudes attached to a condition or to the people living with it. Beliefs about HIV can lead to people living with HIV being judged, avoided, or mistreated — and that stigma harms health and well-being. Accurate information, like U=U, and person-first language help dismantle it. [97]
Suppressed / Virally Suppressed (Viral suppression; virologic control)
A very low viral load on effective ART. CDC uses less than 200 copies/mL for viral suppression; maintaining this prevents sexual transmission. Definitions can differ in other programs, and suppression is not a cure. Ongoing treatment and viral-load monitoring remain necessary. [98]
Syringe Services Program (SSP) (SSP; needle exchange)
A program providing sterile injection equipment, safe disposal and connections to testing, prevention and treatment. Research supports SSPs as an effective way to reduce harms and infections. Services vary, and participation does not guarantee a particular individual reduction in risk. [99]

T

Test-and-Treat (Treat all)
Offering ART to everyone with HIV rather than waiting for a CD4 threshold. WHO’s treat-all recommendation expanded clinical eligibility, but appropriate timing still requires evaluation, and program access or administrative rules do not disappear. Effective ART protects health and prevents sexual transmission when suppression is maintained. [100]
Treatment as Prevention (TasP) (TasP)
Using HIV treatment itself as prevention. A person living with HIV who takes ART and keeps an undetectable viral load cannot pass HIV to sex partners. TasP also improves quality of life and lifespan, which is why global guidance recommends treatment for everyone living with HIV. [101]
Treatment Cascade (HIV care continuum; HIV continuum of care)
A way of describing the steps of HIV care: getting diagnosed, finding the right care, starting ART, staying on treatment, and staying in care — with viral suppression as the goal. Programs also use it to see where people fall out of care so they can fix those gaps. [102]
Treatment Naive (ARV-naive)
A person who has not previously received ART for HIV treatment. This helps guide regimen selection, but it does not prove that the virus is drug-sensitive: transmitted resistance or prior antiretroviral exposure through PrEP/PEP can matter. Resistance and hepatitis B testing inform the initial choice. [103]
Truvada (emtricitabine/tenofovir disoproxil fumarate (FTC/TDF))
A combination pill containing emtricitabine and tenofovir disoproxil fumarate, FDA-approved on August 2, 2004. As HIV treatment it is taken alongside at least one other medicine, and it is also a long-standing daily PrEP option. Generic versions are available, which can make it a lower-cost choice. [104]
Tuberculosis (TB)
A bacterial infection that spreads through the air when a person with active TB coughs, sneezes, speaks, or sings. It usually affects the lungs but can reach the kidneys, spine, or brain. TB comes in two forms — latent TB and TB disease — and in people with HIV, TB disease is an AIDS-defining condition. Both forms are treatable. [105]
Two-Drug Regimen (Dual therapy)
A complete ART regimen containing two active medicines. NIH recommends dolutegravir/lamivudine for selected people starting treatment, subject to viral-load, hepatitis B and resistance criteria and prior PrEP history. March 2026 perinatal guidance also lists it as an Alternative for selected pregnancies; it is not categorically prohibited during pregnancy. [106]

U

U=U (Undetectable = Untransmittable)
Undetectable equals untransmittable: maintaining viral load below 200 copies/mL on ART prevents sexual transmission of HIV. It does not guarantee zero transmission through breastfeeding or shared injection equipment. Continue treatment and monitoring; U=U supports health, informed choices and freedom from stigma. [107]
Undetectable Viral Load
A viral load below a laboratory test’s detection limit. The limit depends on the assay; “undetectable” is not a single universal number. Maintained suppression below 200 copies/mL supports sexual U=U even if a sensitive assay detects a smaller amount. HIV remains in the body, so treatment continues. [108]

V

Viral Load (HIV RNA level; VL)
The amount of HIV in a sample of blood, reported as copies of HIV RNA per milliliter. A main goal of HIV treatment is to bring your viral load down to undetectable — too low for the test to find. Viral load tests also help diagnose recent HIV and guide treatment choices. [109]
Viral Rebound (Rebound)
A confirmed rise in viral load after suppression. NIH defines virologic rebound as confirmed HIV RNA of at least 200 copies/mL after suppression. One isolated detectable result is not enough to establish rebound or treatment failure. Clinical review considers adherence, access, interactions and resistance without blame. [110]

W

Window Period
The interval after exposure before a test can usually detect HIV. CDC’s usual windows are 10–33 days for NAT, 18–45 days for a venous laboratory antigen/antibody test, 18–90 days for a rapid fingerstick antigen/antibody test, and 23–90 days for antibody tests. PrEP/PEP can affect follow-up; a negative result during the window may miss infection. [111]

Sources & references

Sources checked September 21, 2026. Each numbered reference returns to its definition.

  1. 340B Drug Pricing Program (340B) — Source. Checked September 21, 2026. ↩ Definition
  2. ACA (Affordable Care Act) HIV Provisions (ACA; Obamacare) — Source. Checked September 21, 2026. ↩ Definition
  3. Acute HIV Infection (Primary HIV infection; Stage 1 HIV) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  4. ADAP (AIDS Drug Assistance Program) — Source. Checked September 21, 2026. ↩ Definition
  5. Adherence — Source. Checked September 21, 2026. ↩ Definition
  6. AIDS (Acquired Immunodeficiency Syndrome; Stage 3 HIV) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  7. Antibody (Immunoglobulin) — Source. Checked September 21, 2026. ↩ Definition
  8. Antigen/Antibody Test (Ag/Ab combination test; combo test) — Source. Checked September 21, 2026. ↩ Definition
  9. Antiretroviral Therapy (ART) (HIV treatment; combination therapy; HAART) — Source 1. Source 2. Source 3. Checked September 21, 2026. ↩ Definition
  10. Apretude (cabotegravir extended-release injectable (CAB-LA for PrEP)) — Source. Checked September 21, 2026. ↩ Definition
  11. Baseline Testing (Baseline labs) — Source. Checked September 21, 2026. ↩ Definition
  12. Biktarvy (bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF)) — Source. Checked September 21, 2026. ↩ Definition
  13. Cabenuva (cabotegravir/rilpivirine (CAB/RPV)) — Source. Checked September 21, 2026. ↩ Definition
  14. Capsid Inhibitor (Lenacapavir; Sunlenca; Yeztugo) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  15. CCR5 Antagonist (CCR5 inhibitor) — Source. Checked September 21, 2026. ↩ Definition
  16. CD4 Count (CD4 cell count; T-cell count) — Source. Checked September 21, 2026. ↩ Definition
  17. CD4 Percentage (CD4 cell percentage) — Source. Checked September 21, 2026. ↩ Definition
  18. Clinical Trial (Interventional study) — Source. Checked September 21, 2026. ↩ Definition
  19. Coinfection — Source. Checked September 21, 2026. ↩ Definition
  20. Comorbidity (Comorbid condition) — Source. Checked September 21, 2026. ↩ Definition
  21. Condomless Sex — Source 1. Source 2. Source 3. Checked September 21, 2026. ↩ Definition
  22. Confirmatory Test (Supplemental test; follow-up test) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  23. Criminalization (HIV criminalization) — Source 1. Source 2. Source 3. Checked September 21, 2026. ↩ Definition
  24. Descovy (emtricitabine/tenofovir alafenamide (FTC/TAF)) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  25. Diagnosed vs Undiagnosed HIV (Knowledge of status) — Source. Checked September 21, 2026. ↩ Definition
  26. Disclosure — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  27. Dovato (dolutegravir/lamivudine (DTG/3TC)) — Source. Checked September 21, 2026. ↩ Definition
  28. DoxyPEP (Doxycycline post-exposure prophylaxis) — Source. Checked September 21, 2026. ↩ Definition
  29. Drug Resistance (Resistance) — Source. Checked September 21, 2026. ↩ Definition
  30. EHE (Ending the HIV Epidemic in the U.S.) — Source. Checked September 21, 2026. ↩ Definition
  31. EHE Jurisdictions (EHE priority jurisdictions) — Source. Checked September 21, 2026. ↩ Definition
  32. ELISA (Enzyme-Linked Immunosorbent Assay; enzyme immunoassay) — Source. Checked September 21, 2026. ↩ Definition
  33. Elite Controller (Long-term non-progressor) — Source. Checked September 21, 2026. ↩ Definition
  34. Entry Inhibitor — Source. Checked September 21, 2026. ↩ Definition
  35. Enzyme Immunoassay (EIA) (EIA; ELISA) — Source. Checked September 21, 2026. ↩ Definition
  36. False Negative — Source. Checked September 21, 2026. ↩ Definition
  37. Fourth-Generation Test (4th-generation antigen/antibody immunoassay) — Source. Checked September 21, 2026. ↩ Definition
  38. Fusion Inhibitor — Source. Checked September 21, 2026. ↩ Definition
  39. Genotype Test (Genotypic antiretroviral resistance test (GART)) — Source. Checked September 21, 2026. ↩ Definition
  40. Getting to Zero (Zero new infections, zero discrimination, zero AIDS-related deaths) — Source. Checked September 21, 2026. ↩ Definition
  41. Global Fund (The Global Fund to Fight AIDS, Tuberculosis and Malaria) — Source. Checked September 21, 2026. ↩ Definition
  42. Harm Reduction — Source. Checked September 21, 2026. ↩ Definition
  43. Hepatitis B (HBV) (Hepatitis B virus infection) — Source. Checked September 21, 2026. ↩ Definition
  44. Hepatitis C (HCV) (Hepatitis C virus infection) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  45. HIPAA — Source. Checked September 21, 2026. ↩ Definition
  46. HIV (Human Immunodeficiency Virus) — Source. Checked September 21, 2026. ↩ Definition
  47. HIV Drug Resistance Test (Phenotype) (Phenotypic antiretroviral resistance test; phenotypic assay) — Source. Checked September 21, 2026. ↩ Definition
  48. HIV RNA Test (NAT) (Nucleic acid test; NAAT; nucleic acid amplification test) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  49. HIV Test Positivity Rate (Percent positivity) — Source. Checked September 21, 2026. ↩ Definition
  50. HIV-1 vs HIV-2 (HIV type 1; HIV type 2) — Source. Checked September 21, 2026. ↩ Definition
  51. Home HIV Test (HIV self-test; self-testing) — Source 1. Source 2. Source 3. Checked September 21, 2026. ↩ Definition
  52. HOPWA (Housing Opportunities for Persons With AIDS) — Source. Checked September 21, 2026. ↩ Definition
  53. Housing First — Source. Checked September 21, 2026. ↩ Definition
  54. HRSA (Health Resources and Services Administration) — Source. Checked September 21, 2026. ↩ Definition
  55. Immune Reconstitution (Immune Reconstitution Inflammatory Syndrome (IRIS)) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  56. Incidence (New infections) — Source. Checked September 21, 2026. ↩ Definition
  57. Integrase Inhibitor (Integrase strand transfer inhibitor (INSTI)) — Source. Checked September 21, 2026. ↩ Definition
  58. Kaposi Sarcoma (KS) — Source. Checked September 21, 2026. ↩ Definition
  59. Late Diagnosis — Source. Checked September 21, 2026. ↩ Definition
  60. Linkage to Care — Source. Checked September 21, 2026. ↩ Definition
  61. Linkage-to-Care Coordinator (Care navigator; linkage coordinator) — Source. Checked September 21, 2026. ↩ Definition
  62. Long-Acting Injectable (LAI; long-acting ART) — Source 1. Source 2. Source 3. Checked September 21, 2026. ↩ Definition
  63. Long-Term Survivor — Source. Checked September 21, 2026. ↩ Definition
  64. Medicaid — Source. Checked September 21, 2026. ↩ Definition
  65. Molecular Surveillance (HIV cluster detection) — Source. Checked September 21, 2026. ↩ Definition
  66. MPT (Multipurpose Prevention Technology) — Source. Checked September 21, 2026. ↩ Definition
  67. New HIV Diagnoses (HIV diagnoses) — Source. Checked September 21, 2026. ↩ Definition
  68. NNRTI (Non-nucleoside reverse transcriptase inhibitor) — Source. Checked September 21, 2026. ↩ Definition
  69. nPEP (Non-occupational post-exposure prophylaxis) — Source. Checked September 21, 2026. ↩ Definition
  70. NRTI (Nucleoside reverse transcriptase inhibitor) — Source. Checked September 21, 2026. ↩ Definition
  71. oPEP (Occupational post-exposure prophylaxis) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  72. Opportunistic Infection (OI) (OI) — Source. Checked September 21, 2026. ↩ Definition
  73. PEP (Post-exposure prophylaxis) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  74. PEPFAR (President's Emergency Plan for AIDS Relief) — Source. Checked September 21, 2026. ↩ Definition
  75. Person-First Language (Person-centered language) — Source. Checked September 21, 2026. ↩ Definition
  76. PLHIV (People living with HIV) — Source. Checked September 21, 2026. ↩ Definition
  77. Pneumocystis Pneumonia (PCP) (PJP; Pneumocystis jirovecii pneumonia) — Source. Checked September 21, 2026. ↩ Definition
  78. PrEP (Pre-exposure prophylaxis) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  79. PrEP2Prevent (NCT05281393) — Source. Checked September 21, 2026. ↩ Definition
  80. Prevalence — Source. Checked September 21, 2026. ↩ Definition
  81. Protease Inhibitor (PI) (PI) — Source. Checked September 21, 2026. ↩ Definition
  82. Provirus (Proviral DNA) — Source. Checked September 21, 2026. ↩ Definition
  83. Rapid HIV Test (Point-of-care test) — Source. Checked September 21, 2026. ↩ Definition
  84. Rapid Start (Rapid ART initiation; same-day start) — Source. Checked September 21, 2026. ↩ Definition
  85. Recency Testing (Recency assay; RITA) — Source. Checked September 21, 2026. ↩ Definition
  86. Reservoir (Latent HIV reservoir) — Source. Checked September 21, 2026. ↩ Definition
  87. Retention in Care — Source. Checked September 21, 2026. ↩ Definition
  88. Ryan White Parts A/B/C/D/F (RWHAP Parts) — Source. Checked September 21, 2026. ↩ Definition
  89. Ryan White Program (Ryan White HIV/AIDS Program (RWHAP); CARE Act) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  90. Same-Day Start (Same-day ART initiation) — Source. Checked September 21, 2026. ↩ Definition
  91. Sero-prevalence (Seroprevalence) — Source. Checked September 21, 2026. ↩ Definition
  92. Seroconversion — Source. Checked September 21, 2026. ↩ Definition
  93. Serodifferent (Mixed-status couple; serodiscordant) — Source. Checked September 21, 2026. ↩ Definition
  94. Serosorting — Source. Checked September 21, 2026. ↩ Definition
  95. Sexual Health Clinic (STI clinic; STD clinic) — Source. Checked September 21, 2026. ↩ Definition
  96. Single-Tablet Regimen (STR) (STR; fixed-dose combination (FDC)) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  97. Stigma (HIV-related stigma) — Source. Checked September 21, 2026. ↩ Definition
  98. Suppressed / Virally Suppressed (Viral suppression; virologic control) — Source. Checked September 21, 2026. ↩ Definition
  99. Syringe Services Program (SSP) (SSP; needle exchange) — Source. Checked September 21, 2026. ↩ Definition
  100. Test-and-Treat (Treat all) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  101. Treatment as Prevention (TasP) (TasP) — Source. Checked September 21, 2026. ↩ Definition
  102. Treatment Cascade (HIV care continuum; HIV continuum of care) — Source. Checked September 21, 2026. ↩ Definition
  103. Treatment Naive (ARV-naive) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  104. Truvada (emtricitabine/tenofovir disoproxil fumarate (FTC/TDF)) — Source. Checked September 21, 2026. ↩ Definition
  105. Tuberculosis (TB) — Source. Checked September 21, 2026. ↩ Definition
  106. Two-Drug Regimen (Dual therapy) — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  107. U=U (Undetectable = Untransmittable) — Source. Checked September 21, 2026. ↩ Definition
  108. Undetectable Viral Load — Source 1. Source 2. Checked September 21, 2026. ↩ Definition
  109. Viral Load (HIV RNA level; VL) — Source. Checked September 21, 2026. ↩ Definition
  110. Viral Rebound (Rebound) — Source. Checked September 21, 2026. ↩ Definition
  111. Window Period — Source 1. Source 2. Checked September 21, 2026. ↩ Definition

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