It is estimated that AIDS has killed more than 25 million people between 1981 and 2007 and an estimated 33.2 million people worldwide live with HIV as of 2007. Despite recent, improved access to antiretroviral treatment and care in many regions of the world, the AIDS epidemic claimed an estimated 2 million lives in 2007...of which about 270000 were children (figures taken from here).
Visit the official World AIDS Day homepage.