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.
AIDS stands for acquired immunodeficiency syndrome. AIDS is the final stage of HIV infection. It can take years for a person infected with HIV, even without treatment, to reach this stage. Having AIDS means that the virus has weakened the immune system to the point at which the body has a difficult time fighting infections. When someone has one or more of these infections and a low number of T cells, he or she has AIDS.
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 into other parts of the world.
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, and to determine what people
could do to protect themselves. During the early 1980s, as many as
150,000 people became infected with HIV each year. By the early 1990s,
this rate had dropped to about 40,000 each year, where it remains
AIDS cases began to fall dramatically in 1996, when new drugs became available. Today, more people than ever before are living with HIV/AIDS. CDC estimates that about 1 million people in the United States are living with HIV or AIDS. About one quarter of these people do not know that they are infected: not knowing puts them and others at risk.
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 as shaking 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:
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 products is extremely low. The U.S. blood supply is considered among the safest in the world.
You may be at increased risk for infection if you have:
Your risk of getting HIV or passing it to someone else depends on
several things. Do you know what they are? You might want to talk
to someone who knows about HIV. You can also do the following:
• Abstain from sex (do not have oral, anal, or vaginal sex) until you are in a relationship with only one person, are having sex with only each other, and each of you knows the other’s HIV status.
If you do inject drugs, do the following:
The only way to know whether you are infected is to be tested for HIV. You cannot rely on symptoms alone because many people who are infected with HIV do not have symptoms for many years. Someone can look and feel healthy but can still be infected. In fact, one quarter of the HIV-infected persons in the United States do not know that they are infected.
Once HIV enters the body, the body starts to produce antibodies—substances the immune system creates after infection. Most HIV tests look for these antibodies rather than the virus itself. There are many different kinds of HIV tests, including rapid tests and home test kits. All HIV tests approved by the US government are very good at finding HIV.
Many places offer HIV testing: health departments, doctors' offices, hospitals, and sites specifically set up to provide HIV testing.