Acquired immunodeficiency syndrome (AIDS) is a disease of the human immune systems caused by the human immunodeficiency virus (HIV). This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to opportunistic infections and tumors. According to UNAIDs 2010 report, worldwide some 60 million people have been infected, and 33.4 million people are living with HIV. In China, epidemic estimates show that at the end of 2011 there are 780,000 people infected with HIV, with 48,000 new infections and 28,000 deaths. HIV infection continues to be a major global health priority.