An expanded knowledge of immune function has yielded significant breakthroughs in medical technology for manipulating and monitoring the immune system. A highly practical benefit of immunology is administering vaccines and other immune treatments against common infectious diseases such as hepatitis and tetanus that once caused untold sickness and death. Another valuable application of this technology is testing the blood for signs of infection or disease. It is routine medical practice to diagnose such infections as HIV, syphilis, hepatitis B, and rubella by means of immunologic analysis. Both separately and in combination, these methods have made sweeping contributions to individual and community health by improving diagnosis and treatment, and controlling the spread of disease. Many hopes for the survival of humankind lie in our ability to harness the amazing workings of the immune system.