This definition of HIV
HIV
From Wikipedia, the free encyclopedia
Human immunodeficiency virus (
HIV) is a
lentivirus (a member of the
retrovirus family) that causes
acquired immunodeficiency syndrome (AIDS),
[1][2] a condition in
humans in which the
immune system begins to fail, leading to life-threatening
opportunistic infections. Infection with HIV occurs by the transfer of
blood,
semen,
vaginal fluid,
pre-ejaculate, or
breast milk. Within these
bodily fluids, HIV is present as both free virus particles and virus within infected
immune 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 (
perinatal 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 the
World Health Organization (WHO). Nevertheless, complacency about HIV may play a key role in HIV risk.
[3][4] From its discovery in 1981 to 2006, AIDS killed more than 25 million people.
[5] HIV infects about 0.6% of the world's population.
[5] 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 and increasing
poverty.
[6] According to current estimates, HIV is set to infect 90 million people in
Africa, resulting in a minimum estimate of 18 million
orphans.
[7] Antiretroviral treatment reduces both the
mortality and the
morbidity of HIV infection, but routine access to antiretroviral medication is not available in all countries.
[8]
HIV infects primarily vital cells in the human immune system such as
helper T cells (to be specific,
CD4+ T cells),
macrophages, and
dendritic cells.
[9] HIV infection leads to low levels of CD4+
T cells through three main mechanisms: First, direct viral killing of infected cells; second, increased rates of
apoptosis in infected cells; and third, killing of infected CD4+ T cells by
CD8 cytotoxic lymphocytes that recognize infected cells. When CD4+ T cell numbers decline below a critical level,
cell-mediated immunity is lost, and the body becomes progressively more susceptible to opportunistic infections.
Most untreated people infected with HIV-1 eventually develop AIDS.
[10] These individuals mostly die from opportunistic infections or
malignancies associated with the progressive failure of the immune system.
[11] HIV progresses to AIDS at a variable rate affected by viral, host, and environmental factors; most will progress to AIDS within 10 years of HIV infection: some will have progressed much sooner, and some will take much longer.
[12][13] 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 was estimated to be more than 5 years as of 2005.
[14] Without antiretroviral therapy, someone who has AIDS typically dies within a year.
[15]