HIV and AIDS are related, but they are not the same thing. HIV (human immunodeficiency virus) is a sexually transmitted virus that causes illness by gradually breaking down a person’s immune system over the course of years.

AIDS (acquired immunodeficiency syndrome) is the most advanced stage of HIV. In AIDS, the immune system is fully compromised, leaving the body open to a wide range of potentially life-threatening infections. While HIV cannot be cured, it can be effectively controlled with drugs that, if taken early, can prevent progression to AIDS.

How HIV and AIDS Differ

The main difference between HIV and AIDS is that HIV is a virus and AIDS is a stage of HIV infection.

What Is HIV?

HIV is a type of virus called a retrovirus that is passed through intimate contact with body fluids like semen, blood, and vaginal fluids. Once the virus enters the body, it infects a type of white blood cell called a CD4 T lymphocyte (CD4 cell), whose role it is to launch the body’s immune defense.

HIV causes disease by hijacking the genetic machinery of CD4 cells and turning them into HIV-producing factories, churning out millions of new HIV particles before the host cell eventually dies. Over time, as more and more CD4 cells are destroyed, the body becomes less able to recognize and defend itself against infection.

As such, illnesses related to HIV are not caused by the virus but by the breakdown of the body’s immune defenses. This leaves the body vulnerable to an ever-expanding range of opportunistic infections. These are infections rarely seen in people with a healthy immune system.

What Is AIDS?

AIDS is the stage at which the body’s immune defenses are compromised. Technically, this is when the number of CD4 cells per cubic millimeter of blood (cells/mm3) is reduced from normal levels of 500 to 1,500 to less than 200 or the presence of any AIDS-defining condition (opportunistic illnesses that occur more frequently or severely because of immunosuppression).

At this stage, the types of infections the body is vulnerable to are so severe that they can cause death unless HIV treatment is started.

Progression of HIV to AIDS

The symptoms of HIV and AIDS vary by the stage of infection, which are the acute phase, the chronic phase, and AIDS.

Acute Infection

The acute phase is the period immediately following infection, during which flu-like symptoms can develop within two to four weeks. Not everyone infected with HIV will develop acute symptoms, but studies suggest that anywhere from 50% to 90% will.

During the acute phase, symptoms are caused by the launch of the body’s immune defenses, and can include:

The body’s immune defenses eventually control the infection, and symptoms clear (usually within four weeks or more), even if the virus itself is not completely eliminated.

Chronic Infection

The chronic phase follows the resolution of acute HIV symptoms. During this phase, some viral particles remain in circulation at low levels, while others embed themselves in tissues and enter a prolonged latency period (inactivity).

The circulating viruses will continue to multiply, slowly killing more and more CD4 cells, often without notable symptoms. This period can last 10 years or more, although some people may experience faster disease progression.

AIDS

AIDS is the most advanced stage of infection in which the immune system is so severely damaged that it is unable to defend itself against a host of severe opportunistic infections.

People with HIV are diagnosed with AIDS either when their CD4 count is below 200 or they develop any one of two dozen AIDS-defining conditions. These are opportunistic illnesses that occur more frequently or more severely because of immunosuppression.

As opposed to acute HIV symptoms, caused by the activation of the immune system, symptoms of AIDS are often related to opportunistic infections affecting the following areas in the body:

Some of the possible symptoms of AIDS include:

• Chronic diarrhea
• Confusion or dementia
• Difficulty swallowing or painful swallowing
• Extreme, unexplained weight loss
• GI pain
• Nausea and vomiting
• Persistent coughing and shortness of breath
• Seizures or loss of motor control
• Severe headaches
• Vision changes or vision loss

Getting Diagnosed With HIV or AIDS

HIV can be diagnosed at any stage of infection using one of several HIV tests, including:

• Antibody tests: These detect antibodies (immune proteins) produced in response to HIV from either a blood draw, finger stick, or saliva swab. An at-home rapid HIV test is also available.
• Antibody/antigen tests: These lab-based blood tests detect both antibodies and proteins on the surface of the virus called antigens.
• NAAT tests: A nucleic acid test (NAAT) is a lab-based blood test that detects the actual virus by analyzing its genetic material.

AIDS is diagnosed in one of two ways:

• CD4 count: This lab-based test counts the number of CD4 cells in a cubic milliliter of blood. In people with HIV, AIDS can be diagnosed with a CD4 count under 200.
• Other tests: AIDS can also be diagnosed if someone with HIV develops an AIDS-defining illness, irrespective of their CD4 count. This may involve lab and imaging tests that can diagnose bacterial, viral, fungal, and parasitic infections.

Treatment Differences

HIV and AIDS are both treated with antiretroviral drugs. These are oral and injected drugs that block the replication of the virus. By doing so, the virus will drop to undetectable levels, restoring the CD4 count to where the body is better able to fight infection.

There are currently over 25 antiretroviral agents used to control HIV. While most are taken daily by mouth, a combination drug called Cabenuva (cabotegravir/rilpivirine) can control the virus with injections given once every one to two months.

In people with AIDS, other treatments may be needed to manage opportunistic infections. These include antibiotic, antiviral, antifungal, and antiparasitic drugs and medical procedures, such as chemotherapy or radiation for AIDS-defining illnesses like Hodgkin lymphoma or invasive cervical cancer.

Outlook With HIV vs. AIDS

If treated early—before the immune system is compromised—a person newly diagnosed with HIV can expect to live a near-normal to normal life expectancy.

However, if the CD4 count drops below 50, the chances of immune reconstitution are reduced. With a CD4 count this low, a person has a greater than 40% risk of death within one year. With treatment, a person can live for many years, although life expectancy may be reduced by as much as 20 years.

In the absence of antiretroviral therapy, a person may survive anywhere from two to 15 years. By the time AIDS is diagnosed, most people die within three years.

What Is Preventable? 

HIV and AIDS can be prevented in a number of ways:

• HIV can be prevented by practicing safer sex, including a reduction in the number of sex partners and the consistent use of condoms. People at risk of exposure can reduce the risk by taking a form of antiretroviral therapy called pre-exposure prophylaxis (PrEP).
• AIDS can be prevented by starting antiretroviral therapy at the time of diagnosis and taking them as prescribed without interruption.
• AIDS complications can be avoided by taking preventive (prophylactic) drugs when a low CD4 count places you at risk of a severe infection. An example is daily antibiotics used to prevent pneumocystis pneumonia when your CD4 count drops below 200.

When to See a Provider

It is important to see a healthcare provider if you develop signs and symptoms of HIV after a recent sexual exposure or after sharing needles. With that said, many people will not develop symptoms or will mistake the symptoms for some other condition, like the flu.

To this end, the Centers for Disease Control and Prevention (CDC) recommends HIV testing for all people ages 13 to 64 at least once as part of a routine checkup. Those at increased risk should be screened at least annually.

By diagnosing and treating HIV early, you will be better able to prevent AIDS and avoid transmitting it to others.

Summary

HIV is the virus that can lead to AIDS if left untreated. HIV cannot kill a person directly but can lead to life-threatening infections as the body’s immune system is destroyed. AIDS is the stage where the risk of death is high unless antiretroviral therapy is started. With treatment, a person can live for many years and even achieve normal life expectancy.