Human immunodeficiency virus (HIV) attacks the body's immune system, multiplying and spreading from cell to cell at incredible speed, damaging and destroying cells. At first, the immune system fights back by producing new cells, but eventually, HIV causes so much damage that the immune system can no longer keep up. When this happens, T-cells drop below 200 and AIDS develops.
Incidence and Prevalence of HIV
According to the World Health Organization (WHO), approximately 35.3 million people worldwide were living with HIV infection in 2012. Sub-Saharan Africa is the most affected region of the worldnearly 1 in every 20 adults in this area is living with HIV.
In the United States, HIV infection rates remain high in urban minority populations, in men who have sex with men (MSM), and in people who use injection drugs. In November 2012, the Centers for Disease Control and Prevention (CDC) estimated that 1.1 million people in the United States have HIV and about 50,000 people are diagnosed with the disease each year. Also, according to the CDC, about 26 percent of new HIV infections occur in young people between the ages of 13 and 24. In 2010, about 12,000 young people (1,000 per month) were infected with the virus.