Medically Reviewed by Jonathan E. Kaplan, MD on May 21, 2023
4 min read

HIV and AIDS are related, but they’re not the same.

HIV is a virus. It may cause AIDS after you’ve been infected for several years and it’s weakened your immune system.

Not everyone who has HIV will get AIDS. But the infection will advance to AIDS, usually in 10 to 15 years, if you don’t get treatment with antiretroviral drugs.

Many people with the virus don’t know they have it. Of the nearly 1.3 million people in the U.S. who have HIV, more than 160,000 haven’t been diagnosed and aren’t getting treatment.

There are about 36,000 new cases of HIV infection and about 17,000 AIDS diagnoses each year in the U.S.

Worldwide, there were 38.4 million people living with HIV in 2021.

HIV stands for “human immunodeficiency virus.”

“Immunodeficiency” means the systems that fight illnesses in your body aren’t working the way they should.

Your immune system has things called CD4 or T cells that help keep you healthy. HIV attacks these cells. The virus copies itself over and over, killing your CD4 cells. Without them, you’re more likely to get infections from bacteria, viruses, and fungi. Treatment called antiretroviral therapy (ART) lowers the amount of virus in the blood and stops the destruction of these cells.

You can get HIV through direct contact with:

The virus is usually passed from person to person through:

  • Sex
  • Sharing needles or other drug using equipment
  • Mother-to-baby infection during pregnancy

When HIV isn’t treated, it can become AIDS. This stands for “acquired immunodeficiency syndrome.”

It's the third and most advanced stage of HIV infection. People who have AIDS either were never diagnosed with HIV or didn’t get treatment early enough to keep the infection from getting worse.

People with a new HIV infection often feel like they have the flu. Early signs and symptoms include:

If you have these symptoms and might have been exposed to HIV, get tested right away.

Signs that you may have AIDS include:

HIV tests check your blood or fluid from your mouth for antibodies that your body makes in response to the virus. You can take them at a doctor’s office, a community health center, a hospital, or at home.

When you have HIV, your doctor will keep an eye on how much of the virus is in your system. You might hear them call it your “viral load.” Two things will tell them if your infection has become AIDS:

  • Your CD4 count. A person with a healthy immune system has 500 to 1,600 CD4 cells in a cubic millimeter of their blood. A person with AIDS has fewer than 200. This number is called your “CD4 count.”
  • AIDS-defining infections. These are also called opportunistic infections. These generally happen in people who have a CD4 count below 200. Viruses, bacteria, or fungi that don’t usually make healthy people sick can cause these infections in someone with HIV or AIDS.

How long it takes HIV to become AIDS is different for everyone. If you don’t get treatment, it might take 10 to 15 years. With treatment, you may never have AIDS.

More than 30 antiretroviral therapy (ART) drugs are approved to treat the virus. Your doctor will prescribe a mix of these medications.

The drugs will help stop HIV from making copies of itself. That will keep you healthy and lower your risk of spreading it.

There’s no cure for HIV or AIDS. ART’s goal is to lower your viral load and keep your immune system healthy. The idea is to lower the viral load to “undetectable” and keep it that way, by taking your medicine every day as prescribed.

AIDS is the most advanced stage of HIV. The best way to avoid AIDS is to start antiretroviral therapy as soon as possible. Taken every day as prescribed, these drugs will keep you healthy and make your viral level so low, it can’t be detected. Sticking to the right treatment can keep AIDS at bay for years and decades. It also practically eliminates the chances that you’ll pass HIV to your sexual partners and others. Many HIV-positive people live normal life spans.