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HIV Overview

HIV/AIDS: The Basics

(Last updated 9/27/2013; last reviewed 9/27/2013)

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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, vaginal fluids, or breast milk of a person infected with HIV. The most common ways HIV is transmitted are through anal or vaginal sex and sharing of drug injection equipment with a person infected with HIV.
  • The treatment for HIV infection is called antiretroviral therapy (ART). ART involves taking a combination of HIV medicines (called an HIV regimen) every day. 
  • ART can’t cure HIV infection, but it can help people infected with HIV live longer, healthier lives.

What is HIV?

HIV stands for human immunodeficiency virus. HIV is the virus that causes HIV infection. HIV attacks and destroys the infection-fighting CD4 cells of the immune system. Loss of CD4 cells makes it difficult for the body to fight infections and certain cancers.

What is AIDS?

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

How is HIV spread?

HIV is spread through the blood, semen, vaginal fluids, or breast milk of a person infected with HIV. The spread of HIV from person to person is called HIV transmission. 

The most common ways HIV is transmitted are through anal or vaginal sex and sharing of drug injection equipment with a person infected with HIV. 

HIV can pass from an HIV-infected woman to her child during pregnancy or childbirth, or by breastfeeding. This spread of HIV is called mother-to-child transmission of HIV. 

You can’t get HIV by shaking hands or hugging a person infected with HIV. And you can’t get HIV from contact with objects such as dishes, toilet seats, or doorknobs used by a person with HIV.

What is the treatment for HIV?

The treatment for HIV infection is called antiretroviral therapy (ART). ART involves taking 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 destroying infection-fighting CD4 cells, which helps the body fight off infections and certain cancers. ART can prevent HIV infection from advancing to AIDS. 

ART can’t cure HIV, but it can help people infected with HIV live longer, healthier lives. By reducing the amount of HIV in the body, ART also reduces the risk of HIV transmission.

What are the symptoms of HIV/AIDS?

The first signs of HIV infection may be flu-like symptoms, such as fever, headache, and rash. The symptoms may come and go for a month or two after infection. After this earliest stage of HIV infection, more severe symptoms of HIV infection generally don’t appear for many years. 

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

How long does it take for HIV infection to advance to AIDS?

Without treatment, HIV can advance to AIDS. The time it takes for HIV to advance to AIDS varies, but it can take 10 years or more. 

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

  • 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 1,200 cells/mm3.
  • OR
  • An AIDS-defining condition. AIDS-defining conditions include opportunistic infections and cancers that are life-threatening in a person with HIV.

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

  • From the Centers for Disease Control and Prevention (CDC): 
    HIV Basics 
  • From the National Institute of Allergy and Infectious Diseases (NIAID): 
    Understanding HIV/AIDS 

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