Transmissible disease of the immune system caused by HIV. AIDS is the last stage of HIV infection, during which time the individual develops frequently fatal infections and cancers, including Pneumocystis carinii pneumonia, cytomegalovirus (CMV), lymphoma, and Kaposi sarcoma. The first AIDS cases were identified in 1981, HIV was isolated in 1983, and blood tests were developed by 1985. According to the UN's 2004 report on AIDS, some 38 million people are living with HIV, approximately 5 million people become infected annually, and about 3 million people die each year from AIDS. Some 20 million people have died of the disease since 1981. Sub-Saharan Africa accounts for some 70 percent of all HIV infections. Rates of infection are lower in other parts of the world, but the epidemic is spreading rapidly in eastern Europe, India, South and Southeast Asia, Latin America, and the Caribbean.
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In medicine, immunodeficiency (or immune deficiency) is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent. Most cases of immunodeficiency are acquired ("secondary") but some people are born with defects in the immune system, or primary immunodeficiency. Transplant patients take medications to suppress their immune system as an anti-rejection measure, as do some patients suffering from an over-active immune system. A person who has an immunodeficiency of any kind is said to be immunocompromised. An immunocompromised person may be particularly vulnerable to opportunistic infections, in addition to normal infections that could affect everyone.
A number of rare diseases feature a heightened susceptibility to infections from childhood onward. Many of these disorders are hereditary and are autosomal recessive or X-linked. There are over 80 recognised primary immunodeficiency syndromes; they are generally grouped by the part of the immune system that is malfunctioning, such as lymphocytes or granulocytes.
The treatment of primary immunodeficiencies depends on the nature of the defect, and may involve antibody infusions, long-term antibiotics and (in certain cases) stem cell transplantation.
Many specific diseases directly or indirectly impair the immune system. This includes many types of cancer, particularly those of the bone marrow and blood cells (leukemia, lymphoma, multiple myeloma), and certain chronic infections. Immunodeficiency is also the hallmark of acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV). HIV directly attacks the immune system.