According to the Centers for Disease Control and Prevention (CDC), more than 1.1 million adolescents and adults in the United States are estimated to be living with HIV. Around 15 percent are unaware that they have the condition.

People often don’t have any noticeable symptoms at the time that they contract HIV. Many of the symptoms of acute HIV are vague and can mirror other common conditions, so they may not be recognized as HIV symptoms.

When someone is diagnosed with HIV, they may recall having flu-like symptoms months before.

When a person first contracts HIV, they’re said to be in the acute stage. The acute stage is a time when the virus is multiplying very rapidly. At this stage, the immune system activates and tries to fight off HIV.

Symptoms can occur during this stage. If a person knows they’ve been recently exposed to HIV, then they may be prompted to pay attention to their symptoms and seek testing. Acute HIV symptoms are similar to those of other viral infections. They include:

Standard antibody tests may not be able to detect HIV at this stage. A person should seek immediate medical care if they experience these symptoms and think or know that they’ve been recently exposed to HIV.

Alternative tests can be used to identify early HIV transmission. This enables early treatment, which may improve a person’s outlook.

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After the virus becomes established in the body, these symptoms will resolve. This is the chronic stage of HIV.

The chronic HIV stage can last for many years. During this time, a person with HIV may have no obvious symptoms.

However, without treatment, the virus will continue to damage their immune system. This is why early diagnosis and early treatment is now recommended for all people living with HIV. Otherwise, they may eventually develop stage 3 HIV, commonly known as AIDS. Learn more about HIV treatment.

HIV treatment can benefit the health of both HIV-positive people and their partners. If an HIV-positive person’s treatment leads to viral suppression and an undetectable viral load, then they have “effectively no risk” of transmitting HIV, according to the CDC.

If HIV weakens the immune system enough, a person will develop AIDS.

A diagnosis of AIDS means that a person is experiencing immunodeficiency. Their body can no longer effectively fight off many different types of infections or conditions that would have previously been easily dealt with by the immune system.

AIDS doesn’t cause many symptoms itself. With AIDS a person will experience symptoms from opportunistic infections and diseases. These are infections and conditions that take advantage of the body’s decreased immune function.

Symptoms and signs of common opportunistic conditions include:

Specific symptoms will depend on which infections and complications affect the body.

If a person is experiencing any of these symptoms and either has HIV or thinks they may have been exposed to it in the past, they should seek immediate medical advice. Opportunistic infections and diseases can be life-threatening unless treated quickly.

Certain opportunistic conditions, such as Kaposi sarcoma, are extremely rare in people without AIDS. Having one of these diseases may be first the sign of HIV in people who haven’t been tested for the virus.

HIV treatment typically prevents the progression of HIV and the development of AIDS.

If a person thinks they may have been exposed to HIV, they should get tested. Some people may not want to know their HIV status. However, treatment can keep HIV from damaging their body. People with HIV can live long, full lives with the appropriate treatments.

According to the CDC, HIV testing should be part of routine medical care. Everyone between the ages of 13 and 64 should be tested for HIV.