What Is HIV?

Medically Reviewed by Jonathan E. Kaplan, MD on December 11, 2022
14 min read

HIV (human immunodeficiency virus) is a virus that grows in your body and weakens your immune system. This makes it harder to fight off germs and common illnesses.

AIDS (acquired immunodeficiency syndrome) is the last stage of HIV infection.

Someone with HIV is more likely to get sick from things that don’t affect other people. And people with AIDS tend to get serious infections or cancers.

Although there’s no cure, treatment can slow or stop the progress of HIV. Many people who treat HIV live long, healthy lives and never develop AIDS.

HIV came from chimpanzees in Central Africa. Researchers think it may have jumped from them to humans hundreds of years ago. HIV slowly spread across Africa to other parts of the world. It’s been in the U.S. since at least the 1970s.


It’s common to not have symptoms at first, and sometimes even for years or decades. But there are some signs you might develop, such as flu-like symptoms soon after you become infected with HIV. Even if you don’t feel sick, HIV damages the immune system. It hijacks infection-fighting white blood cells called CD4 cells and uses them to churn out thousands of copies of itself. Without treatment, HIV destroys so many of these cells that your body can’t protect you from life-threatening infections. If your CD4 count drops below 200, you have AIDS.

There are three stages of HIV infection:

Stage 1: This is the earliest stage. You may also hear it called the “acute” stage. You might have a feverrashfatiguechills, and other flu-like symptoms. But you might not have any symptoms. If you do, they may start 2-4 weeks after you’re infected. During this time, the virus quickly makes many copies of itself.

Stage 2: During this stage, HIV continues to reproduce, and it slowly damages your immune system over time. You might not feel sick or have symptoms. But HIV isn’t gone, and you can still spread it to other people. This stage can last for years or even decades.

Stage 3: This is when you have AIDS. Your immune system has been severely damaged, leaving you vulnerable to other illnesses.

If you have HIV and you aren’t getting treatment, it’ll weaken your immune system and progress to AIDS. Symptoms of AIDS include:

  • Rapid weight loss
  • Recurring fever or profuse night sweats
  • Extreme and unexplained tiredness
  • Prolonged swelling of the lymph glands in the armpits, groin, or neck
  • Diarrhea that lasts for more than a week
  • Sores of the mouth, anus, or genitals
  • Pneumonia

But each of these symptoms could be related to other illnesses. The only way to know for sure if you have HIV is to get tested.

Anyone can get HIV. You’re at greater risk for it if you:

  • Have more than one sexual partner
  • Have vaginal or anal sex without using a condom
  • Have sex with anyone who has HIV
  • Share needles or syringes with someone who has HIV
  • Have another sexually transmitted infection (STI), such as chlamydiasyphilisgonorrhea, or herpes

Anyone can get HIV through high-risk behaviors. But you’re more likely to get it, or have a harder time getting treatment, if you’re in certain populations.

That’s because some groups face health disparities. Those are differences in care and treatment based on your race, ethnicity, social status, sex, gender, or where you live. 

You may be impacted by HIV more than others if you:

  • Are Black or Latino. You may be part of a community with higher rates of infection. Social, economic, and demographic issues can also cause increased risks in these groups. 
  • Live in the Southern U.S. If you live in a rural area, you may be more likely to face financial hardships or have a hard time finding care nearby.
  • Are in a sexual minority. HIV spreads more easily through anal sex. But things like insurance hurdles, costs, or lack of gender-affirming providers can also affect sexual minorities. Transgender women, along with young Black and Latino men, who have sex with men make up most HIV infections in the U.S. 
  • Are female. Vaginal tissue is typically more vulnerable to infection, which increases risk of infection. But most HIV cases in the U.S. are in males.

These can cause health disparities, and vice versa. For example, you may avoid getting tested for HIV if you think you’ll face discrimination based on your gender identity. Or you may not get care for HIV because you don’t have enough money (or health insurance).

Social determinants of health are the conditions where you live, work, go to school, or play that can affect your health. You’re less likely to get the best HIV diagnosis, care, and treatment if you’re also dealing with: 

  • Substance abuse
  • Mental health disorders
  • Homelessness or housing instability
  • Lack of health care providers
  • Lack of access to health care coverage
  • Racism and discrimination
  • Poverty
  • Shame for having (or getting tested for) HIV
  • Worry about whether you have enough food

There are tools to help you get tested and/or get care for HIV. To find a health center, use the HIV Testing Sites and Care Services Locator.

HIV spreads when an infected person’s blood, semen, or rectal or vaginal fluids get into your bloodstream. The most common ways for this to happen are through unprotected anal or vaginal sex or sharing needles or syringes with an HIV-positive person.

Pregnant women who are HIV-positive can pass the virus to their baby before or during birth. HIV can also pass to a baby through breastfeeding. But the risk is very low for women who take HIV medicine.

It’s possible, but not common, for health care workers to become infected if they have an accidental needle stick while treating someone who has HIV.

There is little to no risk of catching HIV through oral sex. And it’s extremely rare to get it by being bitten by someone infected with HIV. There have been very few cases of that, and those were severe bites that broke the skin.

HIV does not spread through saliva, tears, sweat, hugs, social kissing, or shared food, dishes, or bathrooms.

There’s lots of faulty info out there about the ways you can catch HIV. But it can’t live very long outside someone’s body, like on surfaces. It can’t reproduce, or multiply, outside of a human body either.

If your HIV test is positive, you can start treatment right away. You can also take steps so you don’t spread the virus to others. If you’re pregnant, it’s important to get tested and start treatment as soon as possible.

You can get an HIV test in a doctor’s office, clinic, community health center, hospital, or substance use program.

There are three types of HIV tests:

  • Antibody testThis looks for antibodies – proteins your body makes to fight the virus. The test uses a small blood sample from a vein in your arm or fingerstick. It can also use fluid from inside your mouth (oral fluid test). Fingerstick and oral fluid tests are called rapid tests because you get the results in about 30 minutes or less.
  • Antigen/antibody testThis is the recommended test for HIV. It checks for HIV antibodies as well as parts of the virus called antigens.
  • Nucleic acid test (NAT). This looks for traces of HIV in your blood. Your blood is sent to a lab for testing, so it may take a few days to get the results.

At-home tests. HIV self-tests are available across the U.S. health care workers hope they’ll raise awareness of HIV infection for those who wouldn’t otherwise get tested.  A mouth swab test (called the OraQuick test) can be obtained in pharmacies or online.  It can give a result in 20 minutes. However, a positive test should be confirmed by a laboratory test.   Home specimen collection kits can also be used to see if you have HIV. It can even pick up a recent HIV infection. This kit can be ordered by your doctor, and it’s covered by most insurance plans. It can also be purchased online. It’s mailed to your home. It has everything you need to take a sample of your own blood from a fingerstick. You’ll mail that to a lab, and your test results are sent to your doctor (if your doctor ordered the test) or to you.  Ask your doctor if this test is a good idea for you. 

You won’t know if you have HIV right after you’re infected. It takes time for your body to make antibodies and for antigens to show up.

The “window period” is the time between when you were infected with the virus and when an HIV test can tell you that you have it. This varies from person to person and test to test. Your testing counselor can tell you more about the window period for the test you’re taking. Here are some general guidelines:

An antibody test can detect HIV 23 to 90 days after you’ve become infected with the virus. The window for a test that uses blood from a vein is faster than one that uses oral fluid or blood from a fingerstick.

An antigen/antibody test done in a lab on blood from a vein can detect HIV infection within 18 to 45 days. It takes longer (18 to 90 days) if the test is done with blood from a fingerstick.

A nucleic acid test (NAT) usually has the shortest window: 10 to 33 days. This test is not generally used to diagnose HIV infection unless you have symptoms and a history that suggests you were infected only a few days ago.

If you have a negative test (meaning that it shows that you don’t have HIV) and weren’t exposed to the virus during the window period for that test, you can be certain you didn’t have HIV when you were tested.

If your first test is positive (meaning that it suggests that you have HIV),  a second test should be done to make sure.  If your test was done in a laboratory, this second test will be done automatically. If your first test was done at home or at a community testing site, it’s important to have another blood sample taken and tested in a laboratory.

The CDC recommends that all adults have an HIV test at least once, even if they’re not at risk. If your risk is higher – for example, you have multiple sex partners or use needles for drugs – you should be tested every year.

It’s not uncommon to have other health issues when you have HIV. They might result from your HIV status, (including whether you have AIDS), or from behaviors associated with having HIV (like sex with multiple partners). They include:

Opportunistic infections. Because you have a weakened immune system when you live with HIV (especially if you have AIDS), you’re more likely to also have infections like:

  • Pneumonia, viral infections besides HIV, and thrush. Your risk for opportunistic infections is highest when your CD4 count is below 200. But they also can happen when your CD4 count is below 500.
  • Hepatitis B or hepatitis C, which damages your liver. Like HIV, both types of the hepatitis virus are transmitted through sex or needle sharing.
  • Tuberculosis. TB can seriously affect your lungs and other parts of your body. It’s spread through the air.

AIDS-related cancers. People living with HIV have the highest risk for a type of cancer called Kaposi’s sarcoma. It can form in the lining of your blood and lymph vessels. HIV damages your immune system, which allows the virus causing this cancer to multiply. Its tumors or lesions are usually painless and look like purple spots on your legs, feet, or face. As the cancer gets worse, these lesions can also appear in your genital area, mouth, lymph nodes, digestive tract, and lungs.

Other complications. These can include long-term inflammation that can happen even if your HIV is well-controlled. Over time, chronic inflammation may raise your chances for diabetes; heart, bone, or liver problems; and some types of cancer.

Because of sexual risk behaviors, you may be at risk for other sexually transmitted infections, like syphilis, gonorrhea, chlamydia, or herpes.

You also may have increased risk for depressionanxiety, and other mental disorders. Taking care of your emotional health is particularly important if you live with HIV.

Things have come a long way from the days when there were no treatments for HIV. Today, antiretroviral therapy (ART) can slow down and sometimes stop the progress of the virus, no matter how long you’ve had it.

ART works by lowering your viral load, which is the amount of HIV in your body. The goal is to get it so low that a lab test can’t detect it. With an undetectable viral load, your overall health improves, and you can’t spread the virus to others.

You usually take a combination of at least three HIV meds (called antiretrovirals, or ARVs). Some come in a single pill. It’s important to take them at the right time every day, just as your doctor prescribes.

If you skip doses or go off treatment, your viral load goes up, and so does your ability to infect others.

There are seven types or classes of ARVs, which block HIV in different ways:

Nucleoside reverse transcriptase inhibitors(NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs) block an enzyme called reverse transcriptase. HIV uses this enzyme to make copies of itself.

Protease inhibitors and integrase inhibitors block other copy-making enzymes.

Entry inhibitors (fusion inhibitors, CCR5 antagonists, and post-attachment inhibitors) stop HIV from getting into CD4 cells.

You usually have blood tests 1 month and 3-6 months after you start treatment. These check your viral load and CD4 levels. In time, your viral load should go down and your CD4 count should go up. This means that though you still have the virus, your treatment’s working, and you should stick with it.

Like all drugs, ART can cause side effects. These vary, depending on the person and type of treatment. Even people taking the same HIV drugs can have different side effects. The most common are:

You’re more likely to have these symptoms when you first start treatment, and some may go away in a few weeks. Other side effects can happen over time, including:

A hypersensitivity reaction to an HIV drug called abacavir (included in Triumeq, Trizivir, and Ziagen), which consists of liver damage (hepatotoxicity) or severe skin rashes, can be life-threatening. Call your doctor or get emergency care right away if you think you have a severe reaction to this or any medication you take. Before you start any drug, make sure your doctor explains what side effects to watch out for.

Treatment as prevention. The best way to stay healthy and protect others is to start and stick with treatment. When your viral load is undetectable, you will keep yourself healthy, and there’s no chance you can pass the virus to your sexual partner(s).

There are many ways to prevent or lower your chance of HIV if you don’t already have it:

Safer sex. Use a new condom the right way every time you have anal or vaginal sex. Condoms aren’t 100% effective, so it’s a good idea to use other preventive measures, too. There’s almost no chance of HIV infection with oral sex, but you can get other STDs, like gonorrhea and chlamydia.

Pre-exposure prophylaxis (PrEP). Emtricitabine/tenofovir is a daily pill that helps prevent infection in people who don’t have HIV but are at high risk of getting it. This includes men who have sex with men, women and men who have sex with someone who has HIV, and people who inject drugs. For it to work, you must take it every day. And you should still use condoms to prevent STDs.

A long-acting injectable form of PrEP (long-acting cabotegravir, or Apretude), which can be given every 2 months, is becoming more available.

Post-exposure prophylaxis (PEP). ART helps prevent infection if you take it right after you’ve been exposed to HIV. For it to work, you must start within 3 days. You continue to take one or two pills a day for 28 days.

Safer drug use. If you inject drugs, use a clean needle every time. Never share needles or works. If you would like help getting off drugs, talk to your doctor or HIV counselor.

Nearly 2 million kids under age 15 are infected with HIV across the world. Most of these are in sub-Saharan Africa. In fact, it's the leading cause of death among preteens and teens there. But the number of new HIV cases in children is declining. 

Most children who have HIV got it from their mothers when they were still in the womb, during the birth process, or from breastfeeding. Women who are tested, and stick with treatment if they're positive, greatly lower the chance of passing the virus to their babies. This is the best way to prevent HIV in children.

They can also get HIV through rape or other intercourse at a young age. The younger a child is when they have sex for the first time, the higher their risk for HIV. They also might get HIV from injected drug use or blood transfusions, especially in poorer countries. The U.S. and Western European countries have medical safeguards to prevent HIV transmission through transfusions. 

Not all children with HIV will have symptoms, and those that do won't have exactly the same ones. Symptoms can vary by age.

Some of the more common symptoms are:

Children with HIV get pretty much the same treatment as adults: a combination of medications called ART (antiretroviral therapy). But some HIV drugs don't come in a liquid form that babies and small children can swallow. And some drugs cause serious side effects for kids. 

But with ART, complications from HIV or opportunistic infections may be minimal and can be treated like typical childhood illnesses. With the right combination of drugs and loving support, many kids with HIV can live long and fulfilling lives.

Show Sources


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