What Is HIV and AIDS? Causes, Symptoms & Treatment Options in the USA
Updated: Sep 2
Written by Elizabeth Chernoby in TheSkyMeds Editorial Standards
Medically reviewed by Jonathan Reed, Medical Content Reviewer Feb 5 2026
What Is HIV and AIDS? HIV, or human immunodeficiency virus, is a virus that attacks important cells of the immune system, while AIDS is the most advanced stage of HIV infection when immune damage becomes severe. HIV can be transmitted through certain body fluids, most commonly during anal or vaginal sex without effective prevention or through shared injection equipment. HIV is not spread by ordinary contact such as hugging, sharing toilets, or eating with someone who has the virus. Some people develop flu-like symptoms shortly after infection, but others have no symptoms, so testing—not symptoms—is the only reliable way to determine HIV status. There is currently no cure, but modern antiretroviral therapy can suppress HIV, protect the immune system, prevent progression to AIDS, and allow people with HIV to live long, healthy lives. In the USA, treatment is recommended for everyone diagnosed with HIV and should begin as soon as possible. This guide explains causes, transmission, symptoms, stages, testing, current treatment options, and practical prevention strategies.
What Is HIV and AIDS, and What Is the Difference?
HIV is the virus that causes HIV infection. AIDS—acquired immunodeficiency syndrome—is the late stage that can develop when untreated HIV has severely weakened the immune system.
Having HIV does not automatically mean a person has AIDS. With effective modern treatment, most people living with HIV in the United States do not progress to AIDS.
The HIV.gov explanation of HIV and AIDS clearly distinguishes HIV infection from AIDS and explains how treatment changes the course of the disease.
What does HIV do to the immune system?
HIV primarily targets immune cells called CD4 T cells. These cells help coordinate the body's defense against infections.
Without treatment, ongoing HIV replication can gradually reduce immune function. As immune defenses weaken, infections and illnesses that are normally easier to control can become much more serious.
Antiretroviral therapy suppresses HIV replication and allows immune function to be preserved or recover.
When is HIV considered AIDS?
In the United States, HIV infection is considered to have progressed to AIDS when the CD4 count falls below 200 cells per cubic millimeter of blood or when certain AIDS-defining opportunistic illnesses occur, regardless of CD4 count.
An opportunistic infection is an infection that becomes more likely or more severe when the immune system is significantly weakened.
Effective ART can still provide major benefits even when a person is diagnosed at the AIDS stage.
Is AIDS a separate infection you can catch?
No. People do not “catch AIDS” from another person.
AIDS is a stage of HIV infection caused by severe immune-system damage. HIV is the transmissible virus.
This distinction is important because modern treatment can stop HIV from progressing to AIDS.
What Causes HIV and How Is It Transmitted?
HIV infection occurs when virus-containing body fluids reach vulnerable tissue or enter the bloodstream.
In the United States, the most common routes are anal or vaginal sex and sharing needles, syringes, or other injection equipment.
HIV can also be transmitted during pregnancy, childbirth, or breastfeeding, although treatment can reduce these risks dramatically.
Which body fluids can transmit HIV?
Transmission requires certain body fluids from a person with HIV to contact a mucous membrane, damaged tissue, or the bloodstream.
Important transmission routes involve blood, semen, vaginal or rectal fluids, and breast milk in appropriate exposure circumstances.
Risk varies considerably depending on the type of exposure, viral load, use of condoms, use of HIV prevention medicines, and whether a person with HIV is taking effective treatment.
How is HIV not transmitted?
HIV is not spread through normal everyday social contact.
You do not get HIV from:
hugging or shaking hands;
sharing toilets;
sharing plates, cups, or eating utensils;
sweat or tears;
mosquitoes or other insects;
drinking fountains;
closed-mouth social kissing; or
touching someone with HIV.
HIV is also not transmitted through healthy, unbroken skin.
What does U=U mean?
U=U means Undetectable = Untransmittable.
A person with HIV who takes ART as prescribed and gets and keeps an undetectable viral load does not sexually transmit HIV to their partners. This conclusion is supported by strong evidence and is a central part of modern HIV care.
An undetectable viral load does not mean HIV has been eliminated from the body. Treatment must continue to maintain suppression.
An HIV diagnosis today is very different from an HIV diagnosis decades ago. Effective treatment can suppress the virus to undetectable levels, preserve health, prevent progression to AIDS, and eliminate the risk of sexual HIV transmission as long as viral suppression is maintained.
What Are the Symptoms and Stages of HIV?
HIV symptoms vary widely, and some people have no noticeable symptoms for years. Because common infections can cause similar symptoms, symptoms alone cannot confirm or rule out HIV.
Without treatment, HIV generally progresses through acute infection, chronic infection, and eventually AIDS. Effective treatment can prevent this progression.
What are the early symptoms of HIV?
Approximately two-thirds of people experience flu-like symptoms during acute HIV infection, usually within about two to four weeks after infection.
Possible symptoms include:
fever;
chills;
rash;
night sweats;
muscle aches;
sore throat;
fatigue;
swollen lymph nodes; and
mouth ulcers.
These symptoms can last several days to several weeks. Some people have no symptoms at all.
A fever or rash after sex therefore does not prove HIV infection. Testing is necessary.
What happens during chronic HIV infection?
After the acute stage, HIV can enter a chronic phase in which the virus remains active but symptoms may be mild or absent.
Without treatment, this stage can last for years. A person can still transmit HIV during this period when the virus remains detectable.
With effective ART, people can remain healthy for decades and avoid progression to AIDS.
What symptoms can occur with AIDS?
Advanced HIV can produce serious illness because the immune system is no longer able to control certain infections and diseases effectively.
HIV.gov lists possible symptoms of advanced disease including:
unexplained weight loss;
recurring fever or severe night sweats;
extreme unexplained fatigue;
prolonged swollen lymph nodes;
diarrhea lasting more than a week;
sores of the mouth, anus, or genitals;
pneumonia;
unusual skin or mouth lesions; and
neurological problems.
These symptoms can also result from other conditions, so diagnosis still requires appropriate testing and medical evaluation.
Stage | What is happening | Possible symptoms | Why it matters |
Acute HIV infection | Virus multiplies rapidly soon after infection | Fever, rash, sore throat, swollen glands, fatigue—or no symptoms | Viral load can be high and transmission risk can be substantial |
Chronic HIV infection | Virus remains active over a longer period | Often few or no symptoms | Untreated immune damage continues gradually |
AIDS | Immune system is severely damaged | Opportunistic infections, weight loss, fever, severe fatigue and other illnesses | Requires urgent HIV treatment and management of associated infections |
HIV controlled with ART | Viral replication is strongly suppressed | Many people feel well | Can prevent progression to AIDS and maintain long-term health |
How Is HIV Diagnosed and When Should You Get Tested?
An HIV test is the only reliable way to know whether you have HIV. Modern testing can detect infection much earlier than older tests, but no test identifies every infection immediately after exposure.
There are three main categories: antibody tests, antigen/antibody tests, and nucleic acid tests, or NATs.
The CDC clinical guidance on HIV testing explains the different tests and their detection windows.
How soon after exposure can HIV be detected?
The testing window depends on the test.
According to CDC guidance, in people not taking antiretroviral medicines:
a NAT can usually detect HIV about 10–33 days after exposure;
a laboratory antigen/antibody blood test can usually detect infection about 18–45 days after exposure;
finger-stick antigen/antibody testing may take 18–90 days; and
antibody-only tests usually detect HIV about 23–90 days after exposure.
Testing too early can therefore produce a negative result even when infection occurred.
What happens if an HIV test is positive?
A reactive screening test is followed by appropriate confirmatory testing.
If HIV is confirmed, the person should be linked to HIV medical care and start ART as soon as possible. Current U.S. guidelines recommend treatment for everyone with HIV.
Clinical evaluation commonly includes viral-load measurement, CD4 count, resistance testing, screening for other infections, and assessment of kidney, liver, medication, and general health factors.
What if a possible exposure happened very recently?
Do not wait for symptoms.
If a potentially significant HIV exposure occurred within the last 72 hours, seek medical care immediately to discuss PEP, or post-exposure prophylaxis.
CDC guidance states that PEP must be started within 72 hours, and earlier treatment is preferable. When prescribed, the course generally lasts 28 days.
What Are the HIV Treatment Options in the USA?
HIV is treated with antiretroviral therapy (ART), a combination of medicines that blocks different stages of HIV replication. ART does not currently eliminate HIV from the body, but it can reduce the viral load to extremely low or undetectable levels.
Current U.S. Department of Health and Human Services guidelines recommend ART for all people with HIV and recommend starting treatment immediately or as soon as possible after diagnosis.
The current U.S. HIV antiretroviral treatment guidelines provide federally approved evidence-based recommendations for treating adults, adolescents, children, and pregnant people with HIV.
What medicines are used to treat HIV?
Modern HIV treatment generally combines drugs from different antiretroviral classes.
Major drug classes include:
integrase strand transfer inhibitors, or INSTIs;
nucleoside/nucleotide reverse transcriptase inhibitors, or NRTIs;
non-nucleoside reverse transcriptase inhibitors, or NNRTIs;
protease inhibitors;
entry and attachment inhibitors; and
capsid inhibitors in selected treatment settings.
A person's first regimen is chosen according to current guidelines, resistance results, other medical conditions, drug interactions, pregnancy considerations, kidney and liver health, and personal treatment needs.
HIV.gov notes that many initial regimens combine two or three medicines into a single daily tablet. Long-acting injectable treatment is also available for selected people who meet specific requirements.
How quickly can treatment make HIV undetectable?
Most people taking effective ART as prescribed can achieve viral suppression, and many reach an undetectable viral load within several months.
HIV.gov states that almost everyone who takes treatment as prescribed can become undetectable, usually within about six months after beginning therapy.
Individual response varies, so viral-load testing is used to confirm whether treatment is working.
Does treatment have to continue for life?
With currently available therapy, yes.
Stopping ART allows HIV to begin replicating again and can increase the risk of immune damage, illness, HIV transmission, and drug resistance.
Treatment regimens can be changed when necessary because of side effects, drug interactions, resistance, pregnancy, other illnesses, or convenience—but those changes should be managed by an HIV clinician.
Treatment approach | General role | Practical point | Important limitation |
Daily oral ART | Standard approach for many people | Combination medicines may be available in one tablet | Must be taken consistently |
Integrase inhibitor-based regimens | Common component of recommended modern therapy | Highly effective viral suppression in appropriate patients | Exact regimen depends on clinical factors |
Other oral ART combinations | Used when clinically appropriate | Multiple drug classes allow individualized treatment | Interactions and resistance matter |
Long-acting injectable ART | Option for selected people | May reduce daily pill burden | Not appropriate for every newly diagnosed patient |
Opportunistic-infection treatment or prevention | Used when immune suppression is significant | Protects against specific infections | Does not replace ART |
Treatment monitoring | Viral load, CD4 count and safety labs | Confirms response and guides care | Ongoing medical follow-up remains necessary |
How Can HIV Be Prevented in the USA?
Modern HIV prevention combines testing, condoms, safer injection practices, HIV treatment, PrEP, and emergency PEP when appropriate.
One of the most important advances is treatment as prevention: maintaining an undetectable viral load prevents sexual transmission of HIV.
What is PrEP?
PrEP, or pre-exposure prophylaxis, is HIV-prevention medication for people who do not have HIV but may be exposed through sex or injection drug use.
PrEP options include pills and injections. CDC states that PrEP greatly reduces the chance of acquiring HIV when used appropriately.
PrEP does not prevent pregnancy or other sexually transmitted infections, so condoms may still have an important role.
What is PEP?
PEP is emergency HIV prevention used after a possible exposure.
It must be started within 72 hours, and every hour matters. CDC recommends seeking help promptly from a healthcare professional, emergency department, or urgent-care service after a qualifying exposure.
PEP is designed for emergencies rather than frequent recurring exposure; people with ongoing risk may be better candidates for PrEP.
Can people with HIV have relationships without transmitting HIV sexually?
Yes.
A person with HIV who takes treatment consistently and maintains an undetectable viral load does not sexually transmit HIV.
Regular viral-load monitoring remains important because U=U depends on maintaining viral suppression.
This evidence has transformed HIV care by allowing people living with HIV to have healthy relationships and sex lives without fear of sexually transmitting the virus when sustained undetectability is confirmed.
Safety: When Should You Seek Testing or Urgent Medical Care?
Seek immediate medical advice if you may have had a significant HIV exposure within the previous 72 hours, because PEP is time-sensitive and works best when started as early as possible. Do not wait for symptoms before asking about PEP.
Arrange HIV testing after a potential exposure even if you feel completely well. Early infection can cause no symptoms, and flu-like symptoms cannot distinguish HIV from many other illnesses.
Anyone with a confirmed positive HIV result should be linked to HIV care promptly. Current U.S. guidance recommends starting ART as soon as possible rather than waiting for symptoms or severe immune suppression.
People already receiving ART should contact their HIV clinician if they are having difficulty taking medication, experiencing significant side effects, or considering stopping treatment. Severe illness, breathing difficulty, neurological symptoms, persistent high fever, or symptoms of a serious opportunistic infection require prompt medical assessment.
Conclusion
What Is HIV and AIDS? HIV is a lifelong viral infection that attacks the immune system, while AIDS is the advanced stage that can develop when HIV remains untreated and immune damage becomes severe.
Modern ART has transformed the outlook: treatment can suppress the virus, prevent progression to AIDS, support a long and healthy life, and prevent sexual transmission when an undetectable viral load is maintained.
If you believe you may have been exposed to HIV, testing is more useful than judging symptoms. Seek urgent advice about PEP if the exposure occurred within 72 hours, and discuss PrEP if future exposure is an ongoing possibility. Confirmed HIV should be treated promptly with an individualized regimen under qualified U.S. HIV care.
Frequently Asked Questions
1 . Can you have HIV without knowing it?
Yes. Some people have no symptoms during early or chronic HIV infection and may feel healthy for years. Symptoms cannot reliably confirm or exclude HIV. The only way to know your status is through appropriate HIV testing after the relevant window period.
2 . Is HIV the same thing as AIDS?
No. HIV is the virus, while AIDS is the most advanced stage of HIV infection after severe immune damage. Effective antiretroviral treatment can prevent HIV from progressing to AIDS, and most treated people with HIV in the United States do not develop AIDS.
3 . Can HIV be cured completely in 2026?
No broadly available treatment currently cures HIV. However, modern ART can suppress the virus to undetectable levels and allow people to live long, healthy lives. Maintaining an undetectable viral load also prevents sexual transmission of HIV.
4 . How soon can an HIV test detect infection?
Detection depends on the test. CDC estimates about 10–33 days for NATs and 18–45 days for laboratory antigen/antibody tests using venous blood. Antibody-only tests can take 23–90 days. Testing advice should consider the exposure date and test used.
5 . Can someone with undetectable HIV transmit it during sex?
No. Studies show that people with HIV who take ART and maintain an undetectable viral load do not sexually transmit HIV. This is known as Undetectable = Untransmittable, or U=U. Regular treatment and viral-load monitoring are essential to maintain that protection.
6 . What should I do if I was exposed to HIV yesterday?
Seek medical care immediately and ask about PEP. CDC states that PEP must begin within 72 hours after a possible HIV exposure, and starting sooner is better. Do not delay treatment while waiting for symptoms or for a later HIV test.
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