HIV is a virus that targets the immune system. The signs and symptoms differ depending on the body’s stage of infection.

Around 1.2 million people in the United States are living with HIV, but many are not aware of their status, partly due to a lack of symptoms. Researchers estimate that nearly 1 in 8 people with HIV do not know they have it.

If a person develops symptoms, the symptoms may initially seem like the flu. The virus may present with:

  • headaches
  • fever
  • muscle aches
  • rashes

After these symptoms fade, HIV may not be obvious again for a decade or more, until it has damaged the immune system so much that the immune system cannot fend off serious infection.

However, there is hope. Modern medications can prevent HIV from weakening the immune system by restricting the virus’s ability to grow within the body.

The production of more effective drug regimens means that people living with HIV can look forward to many years ahead. Few people now develop the latter-stage HIV infection known as AIDS while under appropriate care.

This article looks at the different stages of HIV, its symptoms and transmission, and possible treatments.

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HIV is a virus that targets the body’s immune system. The virus damages and destroys white blood cells called CD4 T cells, which usually help the body fight off infections from:

  • viruses
  • bacteria,
  • fungi

Without treatment, HIV keeps replicating and damages more and more cells, ultimately weakening the immune system and leaving it unable to fight these infections.

However, a treatment known as antiretroviral therapy can reduce the amount of HIV in the blood to very low levels.

When viral levels are low enough to be undetectable, HIV no longer damages the immune system. At this point, there is virtually no risk of transmitting it to other people. In short, undetectable = untransmittable (U=U).

The symptoms experienced by a person living with HIV depend on the body’s stage of infection. Not all individuals will see their condition progress at the same rate or display the same symptoms.

If left untreated, an HIV infection typically goes through three stages:

  • acute infection
  • chronic infection
  • acquired immunodeficiency syndrome (AIDS)

Some people do not experience symptoms for years, or until their condition is very advanced. As a result, people cannot rely on symptoms to tell if they have contracted HIV. The only way to know is by taking a test.

Anyone who thinks they may have been exposed to HIV should speak with a healthcare professional. Information on how to get tested for HIV in the U.S. is available here.

Stage 1: Acute HIV infection

About 2–4 weeks after HIV enters the body, it can show up as symptoms that last for days or weeks.

During this period, people may experience:

  • fever
  • fatigue
  • skin rashes (that usually do not itch)
  • muscle aches
  • night sweats
  • sore throat
  • swollen glands in the throat, groin, or armpits
  • sores or ulcers in the mouth or genitals
  • nausea, vomiting, or both

This is known as the seroconversion period. Seroconversion is when the body begins to produce antibodies against HIV. This is the body’s natural response to detecting an infection.

In this phase, there tends to be a large amount of HIV in the blood. It replicates rapidly, so the risk of transmitting the virus to others is high.

Not everyone develops symptoms at this stage. Others experience mild flu-like symptoms that largely go unnoticed. This means that people can contract HIV without knowing it, which makes testing very important.

If a person thinks they may have been exposed to HIV, it is important to consult with a healthcare professional for advice and to ask them about a preventive medication called post-exposure prophylaxis (PEP).

Healthcare professionals can order tests to check for HIV. Some tests can detect the virus after 10 days, while others must be taken 90 days after exposure. People often need to take more than one test to get accurate results.

Stage 2: Chronic HIV infection

In this second phase, HIV is still reproducing at very low levels within the body, and it continues to damage immune cells. People typically do not experience symptoms or get sick from the virus during this stage.

This stage is also known as asymptomatic HIV infection, or “clinical latency.”

Without medication, the chronic stage of an HIV infection can last for a decade or more. People can still transmit the virus to others during this time.

Antiretroviral therapy slows or stops the progression of HIV. People who take antiretroviral drugs as prescribed may remain in the chronic HIV stage for life and never develop stage 3 HIV.

Stage 3 HIV

Stage 3 HIV, also known as AIDS, is the most advanced stage of infection. This occurs when a person’s immune system is badly damaged and can no longer fight off new infections.

People who take antiretroviral therapy can maintain a low viral load and may never develop stage 3 HIV. Other factors that affect whether this stage occurs include:

  • age
  • genetic predisposition
  • the strain of the virus

Symptoms of stage 3 HIV can include:

  • weight loss
  • night sweats
  • fever
  • chronic diarrhea
  • a persistent cough
  • skin problems
  • mouth problems
  • regular infections
  • serious illness such as end stage organ dysfunction

A healthcare professional may diagnose stage 3 HIV if a person’s CD4 blood count drops below 200 cells per cubic milliliter (cells/mm3), or if they develop an opportunistic infection.

Opportunistic infections are those that take advantage of a weakened immune system. Common opportunistic infections in the U.S. include:

Without treatment, people with stage 3 HIV typically survive an average of 3 years. With treatment, people can recover from serious HIV-related infections and diseases and bring HIV to a manageable level.

Some symptoms differ by sex assigned at birth. Read more about HIV symptoms.

The most common ways people acquire HIV are through anal or vaginal sex or sharing drug injection equipment, such as needles, syringes, or cookers.

A person can contract HIV if certain fluids that contain the virus come into contact with damaged tissue or mucous membranes in the genitals, rectum, or mouth.

Only certain body fluids can pass HIV between people. These fluids are:

  • blood
  • semen or preseminal fluid
  • vaginal fluid
  • rectal fluid
  • breast milk

A baby can contract HIV from a person during pregnancy, childbirth, or breastfeeding. This is less common.

There are many myths about HIV transmission. People do not contract HIV from any of the following:

  • mosquito bites, ticks, or other insects
  • sweat, tears, or saliva
  • hugging, shaking hands, or social kissing
  • sharing bathrooms, food, drinks, or dishes
  • sexual activities, such as touching, that do not involve the exchange of body fluids
  • through the air

Read about the myths and facts of HIV transmission here.

The only way a person can know their HIV status is by taking a test. The Centers for Disease Control and Prevention (CDC) recommends that everyone ages 13–64 get tested for HIV at least once.

There are three types of tests for HIV:

  • Nucleic acid test: This blood test looks for the viral particles (particularly genetic material) in the blood and can reveal a person’s viral load. It involves drawing blood from a vein.
  • Antigen/antibody test: This blood test looks for the presence of antigens or antibodies in the blood, which can signal an HIV infection. It involves either drawing blood or taking a finger prick.
  • Antibody test: This test looks for HIV antibodies in blood or oral fluid. This can involve drawing blood from a vein (for faster detection), taking a finger prick, or using an oral swab.

People can get an HIV test in a healthcare clinic or do a self-test at home.

It is not possible to detect HIV immediately after infection. The time between exposure and when a test can produce accurate results is known as the “window period.” This can be between 10–90 days, depending on the individual and the specific test used.

To ensure an accurate result, a person must take an HIV test after their window period.

If someone thinks they may have been exposed to the virus in the last 72 hours, they should talk with a healthcare professional as soon as possible and ask about post-exposure prophylaxis (PEP), which can be highly effective.

There are many ways HIV-negative people can avoid contracting the virus, and there are many ways that HIV-positive people can avoid transmitting it.

Ways to prevent HIV transfer include the following:

  • Using condoms or other barrier methods correctly when having sex can reduce the risk of transmission.
  • Never sharing needles, syringes, or other drug-injection equipment can help prevent transmission. If a person does share equipment, disinfecting the equipment with bleach can reduce the risk of HIV and hepatitis. The CDC provides advice about cleaning syringes here.
  • People who are more likely to contract HIV can take preexposure prophylaxis (PrEP). When taken as prescribed, these medications are highly effective at preventing the transmission of the virus. Truvada and Descovy are two oral PrEP drugs approved by the Food and Drug Administration (FDA). The FDA has also approved Apretude, an injectable PrEP drug that can be administered by a healthcare professional every 2 months.

People who are HIV-positive can prevent transmitting the virus to others by taking antiretroviral drugs.

Most people who use antiretroviral drugs can get the virus to undetectable levels within 6 months. Once their viral load is undetectable, there is virtually no risk of transmitting the virus to other people.

The U.S. Preventive Services Task Force issued guidelines stating that doctors should only recommend PrEP to people who have recently tested negative for HIV. However, 2021 guidelines recommend that doctors should inform all sexually active people about PrEP for the prevention of HIV infection.

Furthermore, anyone who has been sexually active in the last 6 months and meets at least one of the below criteria can receive PrEP:

  • has an HIV-positive partner
  • inconsistent condom use with a partner
  • has had a sexually transmitted infection (STI) within the last 6 months
  • uses injection drugs and shares equipment, or has a partner who participates in injection drug use

HIV is a virus that gradually weakens the immune system by targeting CD4 cells. The signs and symptoms differ depending on the body’s stage of infection.

People can live with HIV for many years without displaying any symptoms. This is why getting tested for HIV is so important.

With effective treatment, many people living with HIV can enjoy long, healthy lives.