Sida

HIV
HIV stands for human immunodeficiency virus. This is the virus that causes AIDS. HIV is different from most other viruses because it attacks the immune system. The immune system gives our bodies the ability to fight infections. HIV finds and destroys a type of white blood cell (T cells or CD4 cells) that the immune system must have to fight disease.
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Structure of the HumanImmunodeficiency Virus, courtesy of NIAID.
AIDS
Origin of HIV
{draw:frame} Scientists identified a type of chimpanzee in West Africa as the source of HIV infection in humans. The virus most likely jumped to humans when humans hunted these chimpanzees for meat and came into contact with their infected blood. Over several years, the virus slowly spread across Africa and later intoother parts of the world. For more information view our question and answer on the origin of HIV.
Brief History of HIV in the United States
HIV was first identified in the United States in 1981 after a number of gay men started getting sick with a rare type of cancer. It took several years for scientists to develop a test for the virus, to understand how HIV was transmitted between humans, andto determine what people could do to protect themselves.
In 2008, CDC adjusted its estimate of new HIV infections because of new technology developed by the agency. Before this time, CDC estimated there were roughly 40,000 new HIV infections each year in the United States. New results shows there were dramatic declines in the number of new HIV infections from a peak of about 130,000 in the mid1980s to a low of roughly 50,000 in the early 1990s. Results also shows that new infections increased in the late 1990s, followed by a leveling off since 2000 at about 55,000 per year. In 2006, an estimated 56,300 individuals were infected with HIV.
AIDS cases began to fall dramatically in 1996, when new drugs became available. Today, more people than ever before are living with HIV/AIDS. CDCestimates that about 1.1 million persons in the United States are living with HIV or AIDS. An estimated 21% of these persons do not know that they are infected: not knowing puts them and others at risk.
How HIV Is and Is Not Transmitted
HIV is a fragile virus. It cannot live for very long outside the body. As a result, the virus is not transmitted through day-to-day activities such asshaking hands, hugging, or a casual kiss. You cannot become infected from a toilet seat, drinking fountain, doorknob, dishes, drinking glasses, food, or pets. You also cannot get HIV from mosquitoes.
HIV is primarily found in the blood, semen, or vaginal fluid of an infected person. HIV is transmitted in 3 main ways:
Having sex (anal, vaginal, or oral) with someone infected with HIVSharing needles and syringes with someone infected with HIV
Being exposed (fetus or infant) to HIV before or during birth or through breastfeeding
HIV also can be transmitted through blood infected with HIV. However, since 1985, all donated blood in the United States has been tested for HIV. Therefore, the risk for HIV infection through the transfusion of blood or blood productsis extremely low. The US. blood supply is considered among the safest in the world. For more information view our question and answer on blood safety.
New research suggests that HIV infected caregivers may transmit HIV to children through blood found in pre-chewed food; therefore HIV-infected caregivers should avoid pre-chewing food for their infants. For more information view our questions andanswers on transmission.
Risk Factors for HIV Transmission
You may be at increased risk for infection if you have
injected drugs or steroids, during which equipment (such as needles, syringes, cotton, water) and blood were shared with others
had unprotected vaginal, anal, or oral sex (that is, sex without using condoms) with men who have sex with men, multiple...