HIV and AIDS Overview
AIDS (acquired immunodeficiency syndrome) was first identified a quarter of a century ago. Since then, it has become a worldwide pandemic. People with AIDS have weakened immune systems, which make them susceptible to a variety of infections and cancers.
All people with AIDS are infected with HIV (human immunodeficiency virus). HIV is a specific type of virus called a retrovirus. Retroviruses are able to hide from the immune system by inserting their genetic information directly into cells, where they can replicate (make copies of themselves) out of the reach of the immune system.
HIV is an especially effective retrovirus, because it damages or kills CD4 cells (helper T cells). CD4 cells are important immune system cells that fight infection and disease by attacking bacteria, fungi, protozoa, and viruses. As the number of CD4 cells decrease, the immune system weakens and is less able to fight off opportunistic infections (such as tuberculosis or Pneumocystis carinii pneumonia) and cancers.
The CD4 cell count is used to determine when an HIV infection has developed into AIDS. The normal CD4 cell count typically ranges from 500 to 1500 cells per cubic millimeter of blood. According to the Centers for Disease Control and Prevention (CDC), people are diagnosed with AIDS when their CD4 cell counts drop below 200. People infected with HIV with higher CD4 cell counts are also diagnosed with AIDS if they have any of the opportunistic infections associated with AIDS.
It's possible that HIV was infecting people as early as the 1950s. Evidence of people developing rare opportunistic infections in the United States was first noticed in the late 1970s. AIDS was first reported in the United States in 1981 and HIV testing became available in 1985. New treatments developed in the 1990s have slowed the progression of HIV to AIDS, increased quality of life for people living with AIDS, and significantly lowered the number of deaths due to AIDS. Unfortunately, these treatments are less accessible to people in underdeveloped countries.
HIV and AIDS disease statistics can only be estimated. According to the United Nation's AIDS clock, the total worldwide statistics for 2005 are approximately:
- 4 million people newly infected with HIV
- 38 million people living with HIV/AIDS
- 3 million deaths due to AIDS
The CDC's total U.S. estimated statistics for 2005 are approximately:
- 38,000 people newly infected with HIV
- 1 million people living with HIV/AIDS
- 16,000 deaths due to AIDS
Although anyone can become infected with HIV, the disease is more prevalent in certain populations in the United States:
- Men who have sex with men were the largest estimated proportion of people diagnosed with HIV/AIDS, followed by males infected through heterosexual contact.
- Male adults and adolescents make up almost 75% of HIV/AIDS diagnoses.
- African Americans (who comprise approximately 13% of the U.S. population) accounted for about 50% of the estimated number of HIV/AIDS diagnoses.