immunodeficiency virus) is a virus that attacks the
immune system, the body's natural defense system.
Without a strong immune system, the body has trouble fighting off disease. Both
the virus and the infection it causes are called HIV.
White blood cells are an important part of the immune system. HIV infects and
destroys certain white blood cells called CD4+ cells. If too many CD4+ cells
are destroyed, the body can no longer defend itself against infection.
The last stage of HIV infection is
AIDS (acquired immunodeficiency syndrome). People with
AIDS have a low number of CD4+ cells and get infections or cancers that rarely
occur in healthy people. These can be deadly.
But having HIV doesn't mean you have AIDS. Even without treatment, it takes a long time for HIV to
progress to AIDS—usually 10 to 12 years.
When HIV is diagnosed before it becomes
AIDS, medicines can slow or stop the damage to the immune system. If AIDS does develop, medicines can often help the immune system return to a healthier state.
treatment, many people with HIV are able to live long and active lives.
There are two types of
- HIV-1, which causes almost all the cases of
- HIV-2, which causes
an AIDS-like illness. HIV-2 infection is uncommon in North America.
HIV infection is caused by the
human immunodeficiency virus. You can get HIV from contact with infected blood,
semen, or vaginal fluids.
- Most people get the virus by having
unprotected sex with someone who has HIV.
- Another common way of
getting it is by sharing drug needles with someone who is infected with
- The virus can also be passed from a mother to her baby during
pregnancy, birth, or breast-feeding.
HIV doesn't survive well outside the body. So it can't
be spread by casual contact like kissing or sharing drinking glasses with an