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バンクーバー 2006/04/05 19:30:02
Human immunodeficiency virus, commonly known by the initialism HIV, formerly known as HTLV-III and lymphadenopathy-associated virus, is a retrovirus that primarily infects vital components of the human immune system such as CD4+ T cells, macrophages and dendritic cells. It also directly and indirectly destroys CD4+ T cells. As CD4+ T cells are required for the proper functioning of the immune system, when enough CD4+ T cells have been destroyed by HIV, the immune system functions poorly, leading to the syndrome known as AIDS. HIV also directly attacks organs, such as the kidneys, the heart and the brain leading to acute renal failure, cardiomyopathy, dementia and encephalopathy. Many of the problems faced by people infected with HIV result from failure of the immune system to protect from opportunistic infections and cancers.
HIV is transmitted through direct contact of a mucous membrane with a bodily fluid containing HIV, such as blood, semen, vaginal fluid, preseminal fluid or breast milk. This transmission can come in the form of: penetrative (anal or vaginal) sex; oral sex; blood transfusion; contaminated needles; exchange between mother and infant during pregnancy, childbirth, or breastfeeding; or other exposure to one of the above bodily fluids.
AIDS is thought to have originated in sub-Saharan Africa during the twentieth century [1] and is now a pandemic. At the end of 2004, UNAIDS estimated that nearly 40 million people were currently living with HIV [2]. The World Health Organization estimated that the AIDS epidemic had claimed more than 3 million people and that 5 million people had acquired HIV in the same year. Currently it is estimated that 28 million people have died and that it is set to infect 90 million people in Africa, resulting in a minimum estimate of 18 million orphans in Africa alone [2].
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