Overview

The human immunodeficiency virus (HIV) is an infection that damages specific cells of the immune system. HIV makes the body less able to clear out infections and diseases. If HIV infection is not treated, over time it can cause an illness called acquired immunodeficiency syndrome (AIDS).

HIV spreads through contact with some body fluids. The virus can spread during sex, when people share needles or syringes, or during pregnancy, delivery or breastfeeding. The only way to know if you have HIV is to get tested.

HIV is treatable and preventable. Medicine can control HIV levels in the blood. This keeps the infection from getting worse, so some people never get AIDS.

Symptoms

The symptoms of HIV and AIDS vary depending on the person and the stage of infection.

The first stage, when a person gets HIV, can feel like the flu. This infection, called the primary infection or acute HIV, happens around 2 to 4 weeks after the virus enters the body.

Common symptoms of acute HIV include:

  • Fever.
  • Swollen lymph glands, also called nodes, mainly on the neck.
  • Sore throat.
  • Rash.
  • Muscle aches.
  • Diarrhea.
  • Weight loss.

Other symptoms with new HIV infections include headache, joint pain, dry cough, night sweats and mouth sores.

These symptoms can last for days or weeks. Symptoms may be serious, but some people have mild or no symptoms during this stage. Even if symptoms are mild or you don't have symptoms, HIV spreads easily to others during the acute stage.

After the acute stage, symptoms often go away. HIV stays in the body, and the infection enters the next stage, called the clinical latent infection or chronic HIV. This stage can last for many years.

Over time, an HIV infection weakens the body's ability to clear out germs.

People with symptomatic HIV infection may get other infections, such as:

  • Shingles, also called herpes zoster.
  • Yeast infection in the mouth, called thrush.
  • Lung infections called pneumonia.

Symptomatic HIV infection also can cause symptoms that don't go away, including:

  • Fever.
  • Fatigue.
  • Swollen lymph glands.
  • Diarrhea.
  • Weight loss.

Without treatment, an HIV infection continues to damage the immune system.

After 7 to 10 years, the infection can progress to AIDS. People with AIDS are more likely to have infections that would be easily controlled by a working immune system. Some cancers are also more common in people who have AIDS.

Symptoms of AIDS include symptoms from earlier stages of HIV infection, such as fever that keeps coming back, swollen lymph glands, ongoing diarrhea and rapid weight loss.

Other symptoms of AIDS include:

  • Sweats.
  • Chills.
  • White spots or lesions on the tongue or mouth that don't go away.
  • Fatigue.
  • Skin rashes or bumps.

Thanks to treatment for HIV, many people do not develop AIDS.

When to see a doctor

If you might have come into contact with HIV, see a healthcare professional right away. There is medicine that can help stop the virus. This medicine, called post-exposure prophylaxis (PEP), works best if you start taking it within three days after contact with virus.

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Causes

HIV is caused by a virus that attacks white blood cells called CD4 T cells. This weakens the immune system and allows germs to cause infection and disease. The immune system can't clear HIV from the body. That means HIV must be treated with medicine to prevent damage.

People with untreated HIV can spread it through:

  • Sexual contact.
  • Sharing needles or syringes.
  • Contact with blood.
  • During pregnancy, delivery or breastfeeding, from birth parent to child.

Over time, even without symptoms, untreated HIV infection causes CD4 T cell levels to drop. In someone with a typical immune system, there are between 500 and 1,600 CD4 T cells in a blood sample. When the CD4 number falls below 200 cells, HIV infection has progressed to AIDS.

Risk factors

You are more likely to get HIV if you:

  • Are sexually active.
  • Have contact with infected blood.
  • Share needles or syringes.
  • Are diagnosed with a sexually transmitted infection.

HIV can spread through sexual activity, including oral sex. Your risk of getting HIV is higher if your partner has HIV or is at high risk of HIV. This risk goes up if you don't regularly use a condom or other barrier during sexual activity.

Your HIV risk is higher if you have been diagnosed with a sexually transmitted infection, especially syphilis. People who have anal sex also have a higher risk.

For males, the risk of HIV is higher if you are not circumcised.

Other factors that raise a person's risk include bleeding during sex or having sex during a menstrual period. Children born to a parent with untreated HIV have a higher risk of HIV during pregnancy, birth or breastfeeding.

Your HIV risk goes up if you share needles or syringes. Getting a tattoo also may raise your risk of HIV exposure. People in certain jobs with regular exposure to blood may be at higher risk of HIV infection. Also, HIV can be transmitted through blood products or transfusion if blood isn't screened. The risk of getting HIV in this way is very low in the United States because donated blood is screened and tested for HIV.

HIV risk factors do not include casual contact.

  • You cannot get HIV or AIDS by hugging, kissing, dancing or shaking hands with someone who has the infection.
  • Sharing dishes does not spread HIV.
  • Toilet seats do not spread HIV.
  • HIV is not spread through the air, water or insect bites.
  • You cannot get HIV by donating blood.

You can't get HIV from someone's sweat, tears or saliva.

Complications

HIV infection weakens your immune system. The infection makes you much more likely to get many infections and certain types of cancers.

Infections that are linked with HIV and AIDS include:

  • Pneumonia. This includes bacterial pneumonia and Pneumocystis pneumonia (PCP).
  • Candidiasis, also called thrush. Candidiasis is an infection caused by fungus. It causes a thick, white coating on the mouth, tongue, esophagus or vagina.
  • Tuberculosis (TB). This is a bacterial infection that mainly affects the lungs. People with HIV have a higher risk of catching this serious illness.
  • Cytomegalovirus (CMV). This illness, caused by the cytomegalovirus, spreads through body fluids and stays in the body for life after infection. If the immune system weakens, the virus becomes active, causing damage to the eyes, digestive system, lungs or other organs.
  • Cryptococcal meningitis. Meningitis is inflammation of the membranes and fluid around the brain and spinal cord. This form of meningitis, caused by a fungus, is a central nervous system infection linked to HIV.
  • Toxoplasmosis. This infection is caused by the parasite Toxoplasma gondii. It may be a new infection or one from earlier in life that becomes active again. Toxoplasmosis can cause severe lung or brain disease in people with a weakened immune system. Rarely it may show up in other tissues throughout the body.

Cancers linked to HIV and AIDS include:

  • Lymphoma. This type of cancer affects the system of immune organs, glands, vessels and lymph nodes. Symptoms may include swollen lymph nodes in the neck, armpit and groin.
  • Kaposi sarcoma. This is a tumor of the blood vessel walls. Kaposi sarcoma may appear pink, red, purple, brown or black, depending on your skin color. Kaposi sarcoma also can affect the internal organs.
  • Cancers related to human papillomavirus (HPV). There are many strains of HPV. Some are linked to cancer of the vulva, vagina, cervix, anus, penis and throat.

Other complications can include:

  • Wasting syndrome. Untreated HIV/AIDS can cause a great deal of weight loss. Diarrhea and fever often happen with the weight loss.
  • Brain and nervous system complications. HIV can cause brain and nervous system symptoms such as confusion, forgetfulness and difficulty walking. HIV-associated neurological conditions can range from mild symptoms such as behavior changes and reduced mental functioning to severe dementia causing weakness and not being able to function.
  • Kidney disease. HIV-associated nephropathy (HIVAN) is inflammation of the tiny filters in the kidneys. These filters remove excess fluid and waste from the blood and pass them to the urine.
  • Liver disease. Liver disease also is a major complication, mainly in people who also have hepatitis B or hepatitis C.

Prevention

To prevent HIV, take actions that lower your risk of getting HIV, such as:

  • Get tested and treated for any sexually transmitted infections. These types of infections make it easier to get or spread HIV.
  • Ask sexual partners if they have HIV, and tell your partners if you have HIV.
  • Use condoms correctly, every time.
  • Do not share needles or syringes. Use new, sterile equipment each time.
  • If you are pregnant, get medical care that includes an HIV test right away.

Some people may consider having the foreskin of the penis removed, called circumcision. People who have a foreskin seem to get HIV through sexual contact at a higher rate than people who've been circumcised.

Also consider pre-exposure prophylaxis (PrEP). Medicines can be used for what's called pre-exposure prophylaxis, often shortened to PrEP. These medicines help prevent HIV infection when taken as directed among people at high risk.

Some PrEP medicines can be swallowed. Other medicines are given as a shot.

Options may include:

  • Tenofovir disoproxil fumarate and emtricitabine (Truvada). This medicine is a tablet swallowed once a day.
  • Tenofovir alafenamide fumarate and emtricitabine (Descovy). This medicine is a tablet swallowed once a day. It is approved for use by males and transgender women. It is not approved for people who have receptive vaginal sex.
  • Cabotegravir (Apretude). This medicine is given as an injection every two months.
  • Lenacapavir (Yeztugo). The first dose of this medicine is given as both a tablet and injection. After that, the medicine is given by injection only every six months.

Before you start PrEP, your healthcare professional will do an HIV test. This test is repeated every three months. You need to take PrEP pills every day or closely follow the shot schedule. Also, PrEP protects only against HIV. Use safe sex practices and get tested for sexually transmitted infections as recommended.

If you have HIV, taking antiretroviral therapy (ART) as directed can lower the amount of virus in your blood to where it is not detectable by tests. At this level, people are highly unlikely to spread HIV through sex. You may see this referred to as Undetectable = Untransmittable, shortened to U=U.

If you think you've been exposed to HIV, wash the area with soap and water. If there is eye exposure, rinse with water or use an eye wash station for 15 minutes. Then contact your healthcare professional or workplace health resource or go to an emergency room.

After contact or possible contact with HIV, medicines to block HIV are started within the first 72 hours. This is called post-exposure prophylaxis, also known as PEP. These medicines are very effective in lowering your risk of getting HIV. You need to take the medicine for 28 days.

May 22, 2026
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