HIV

Human immunodeficiency virus (HIV) is a lentivirus (a member of the retrovirus family) that causes acquired immudefiency syndrome (AIDS), a condition in humans in which the imunne system begins to fail, leading to life-threatening opportunistic infection. Infection with HIV occurs by the transfer of blood,semen, vaginal fluid, pre-ejaculate, or breast milk. Within theese bodily fluids, HIV is present as both free virus particles and virus within infected imunne cells. The four major routes of transmission are unsafe sex, contaminated needles, breast milk, and transmission from an infected mother to her baby at birth (vertical transmission). Screening of blood products for HIV has largely eliminated transmission through blood transfusions or infected blood products in the developed world.

HIV infection in humans is considered pandemic by WHO. From 1981 to 2006, AIDS killed more than 25 million people. HIV infects about 0.6% of the world's population. In 2005 alone, AIDS claimed an estimated 2.4–3.3 million lives, of which more than 570,000 were children. A third of these deaths are occurring in sub saharan,Africa, retarding economic growth nd increasing poverty. According to current estimates, HIV is set to infect 90 million people in africa, resulting in a minimum estimate of 18 million orphan. Antriretvorial treatment reduces both the mortality and the morbodity of HIV infection, but routine access to antiretroviral medication is not available in all countries.

HIV primarily infects vital cells in the humman immune systemsuch as Helper T cells (specifialy cd4⁺ T cells), Marchopages, and Dendritic cells. HIV infection leads to low levels of CD4⁺ T cells through three main mechanisms: firstly, direct viral killing of infected cells; secondly, increased rates of apoptosis in infected cells; and thirdly, killing of infected CD4⁺ T cells by lymphocites that recognize infected cells. When CD4⁺ T cell numbers decline below a critical level, cell-immediate system is lost, and the body becomes progressively more susceptible to opportunistic infections.

Eventually most HIV-infected individuals develop AIDS. These individuals mostly die from opportunistic infections or malignancies associated with the progressive failure of the immune system. Without treatment, about 9 out of every 10 persons with HIV will progress to AIDS after 10–15 years. Many progress much sooner.Treatment with anti-retrovirals increases the life expectancy of people infected with HIV. Even after HIV has progressed to diagnosable AIDS, the average survival time with antiretroviral therapy (as of 2005) is estimated to be more than 5 years. Without antiretroviral therapy, death normally occurs within a year.

Structure Of HIV