HIV is the cause of AIDS. AIDS is a potentially deadly illness that interferes with the body's ability to fight infection and certain types of cancer. Treatments that contain several drugs (called highly active antiretroviral therapy [HAART]) have greatly improved outcomes for HIV-infected patients. This therapy is expensive and can be difficult to provide to the patients who need it, particularly in developing countries. In 2002, China began a program to provide free HAART to patients who met the national criteria for treatment. Most studies of the outcomes of programs that provide HAART in developing countries have been of short duration (1 year), and whether the benefits seen early in the programs continue over time is less clear.