The United States of America is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. USA population is 301.1 millions (July 2007 estimate); the male/female ratio is 0.967 male(s)/female (2007 est.). The birth rate is estimated at 14.16 births and the mortality rate at 8.26 per 1,000 people; the country population growth rate at 0.894%. The life expectancy is 78 years (75.15 years for males and 80.97 years for females). The total fertility rate is 2.09 children born per woman, and infant mortality rate is 6.37 deaths/1,000 live births.

The prevalence of HIV/AIDS in adult population was estimated to be 3.2 % (2005), with 1,200,000 people believed to be living with HIV/AIDS and 550,394 have so far died due to the pandemic. There were about 1,411 children living with HIV/AIDS (2005).