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AIDS was first reported in the United States in 1981 and has since become a major worldwide epidemic. AIDS is caused by the human immunodeficiency virus, or HIV. By killing or damaging cells of the body's immune system, HIV progressively destroys the body's ability to fight infections and certain cancers. People diagnosed with AIDS may get life-threatening diseases called opportunistic infections. These infections are caused by microbes such as viruses or bacteria that usually do not make healthy people sick.
Since 1981, more than 980,000 cases of AIDS have been reported in the United States to the Centers for Disease Control and Prevention (CDC). According to CDC, more than 1,000,000 Americans may be infected with HIV, one-quarter of whom are unaware of their infection. The epidemic is growing most rapidly among minority populations and is a leading killer of African-American males ages 25 to 44. According to CDC, AIDS affects nearly seven times more African Americans and three times more Hispanics than whites. In recent years, an increasing number of African-American women and children are being affected by HIV/AIDS.
What are HIV and AIDS?
HIV, or human immunodeficiency virus, is the virus that causes AIDS. HIV attacks the immune system by destroying CD4 positive (CD4+) T cells, a type of white blood cell that is vital to fighting off infection. The destruction of these cells leaves people infected with HIV vulnerable to other infections, diseases and other complications.
AIDS is the final stage of HIV infection. A person infected with HIV is diagnosed with AIDS when he or she has one or more opportunistic infections, such as pneumonia or tuberculosis, and has a dangerously low number of CD4+ T cells (less than 200 cells per cubic millimeter of blood).
How HIV Causes AIDS
HIV destroys CD4 positive (CD4+) T cells, which are white blood cells crucial to maintaining the function of the human immune system. As HIV attacks these cells, the person infected with the virus is less equipped to fight off infection and disease, ultimately resulting in the development of AIDS.
Most people who are infected with HIV can carry the virus for years before developing any serious symptoms. But over time, HIV levels increase in the blood while the number of CD4+ T cells decline. Antiretroviral medicines can help reduce the amount of virus in the body, preserve CD4+ T cells and dramatically slow the destruction of the immune system.
People who are not infected with HIV and generally are in good health have roughly 800 to 1,200 CD4+ T cells per cubic millimeter (mm3) of blood. Some people who have been diagnosed with AIDS have fewer than 50 CD4+ T cells in their entire body.
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