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HIV Overview

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HIV/AIDS: The Basics

Last Reviewed: August 22, 2017

Key Points

  • HIV is the virus that causes HIV infection. AIDS is the most advanced stage of HIV infection.
  • HIV is spread through contact with the blood, semen, pre-seminal fluid, rectal fluids, vaginal fluids, or breast milk of a person with HIV. In the United States, HIV is spread mainly by having anal or vaginal sex or sharing drug injection equipment with a person who has HIV.
  • Antiretroviral therapy (ART) is the use of HIV medicines to treat HIV infection. People on ART take a combination of HIV medicines (called an HIV regimen) every day. 
  • ART can’t cure HIV infection, but it can help people with HIV live longer, healthier lives. HIV medicines can also reduce the risk of transmission of HIV.

What is HIV/AIDS?

HIV stands for human immunodeficiency virus, which is the virus that causes HIV infection. The abbreviation “HIV” can refer to the virus or to HIV infection. 

AIDS stands for acquired immunodeficiency syndrome. AIDS is the most advanced stage of HIV infection.

HIV attacks and destroys the infection-fighting CD4 cells of the immune system. The loss of CD4 cells makes it difficult for the body to fight infections and certain cancers. Without treatment, HIV can gradually destroy the immune system and advance to AIDS.

How is HIV spread?

HIV is spread through contact with certain body fluids from a person with HIV. These body fluids include:

  • Blood
  • Semen
  • Pre-seminal fluid
  • Vaginal fluids
  • Rectal fluids
  • Breast milk

The spread of HIV from person to person is called HIV transmission. The spread of HIV from a woman with HIV to her child during pregnancy, childbirth, or breastfeeding is called mother-to-child transmission of HIV.

In the United States, HIV is spread mainly by having sex with or sharing drug injection equipment with someone who has HIV. To reduce your risk of HIV infection, use condoms correctly and consistently during sex, limit your number of sexual partners, and never share drug injection equipment. 

Mother-to-child transmission is the most common way that children become infected with HIV. HIV medicines, given to women with HIV during pregnancy and childbirth and to their babies after birth, reduce the risk of mother-to-child transmission of HIV. 

You can’t get HIV by shaking hands or hugging a person who has HIV. You also can’t get HIV from contact with objects such as dishes, toilet seats, or doorknobs used by a person with HIV. HIV does not spread through the air or through mosquito, tick, or other insect bites.

What is the treatment for HIV?

Antiretroviral therapy (ART) is the use of HIV medicines to treat HIV infection. People on ART take a combination of HIV medicines (called an HIV regimen) every day. (HIV medicines are often called antiretrovirals or ARVs.) 

ART prevents HIV from multiplying and reduces the amount of HIV in the body. Having less HIV in the body protects the immune system and prevents HIV infection from advancing to AIDS. 

ART can’t cure HIV, but it can help people with HIV live longer, healthier lives. ART also reduces the risk of HIV transmission.

What are the symptoms of HIV/AIDS?

Within 2 to 4 weeks after a person becomes infected with HIV, they may have flu-like symptoms, such as fever, chills, or rash. The symptoms may last for a few weeks after they become infected.

After this earliest stage of HIV infection, HIV continues to multiply but at very low levels. More severe symptoms of HIV infection, such as signs of opportunistic infections, generally don’t appear for many years. (Opportunistic infections are infections and infection-related cancers that occur more frequently or are more severe in people with weakened immune systems than in people with healthy immune systems.)

Without treatment with HIV medicines, HIV infection usually advances to AIDS in 10 years or longer, though it may take less time for some people. 

HIV transmission is possible at any stage of HIV infection—even if a person with HIV has no symptoms of HIV.

How is AIDS diagnosed?

The following criteria are used to determine if a person with HIV has AIDS:

  • The person’s immune system is severely damaged, as indicated by a CD4 count of less than 200 cells/mm3. A CD4 count measures the number of CD4 cells in a sample of blood. The CD4 count of a healthy person ranges from 500 to 1,600 cells/mm3.
    AND/OR
  • The person has developed certain opportunistic infections.

Where can I learn more about HIV/AIDS?

This fact sheet is based on information from the following sources:

  • From CDC: 
    HIV Basics 
  • From the National Institute of Allergy and Infectious Diseases (NIAID): 
    HIV/AIDS

Need Help?

  • Call 1-800-448-0440
  • (1 p.m. to 4 p.m. ET)
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