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Human immunodeficiency virus (HIV) is the virus that causes acquired immune deficiency syndrome (AIDS), a chronic life-threatening condition that damages the cells of the immune system. This prevents the body from fighting off viruses, bacteria, fungi and parasites. People infected with HIV and AIDS are vulnerable to the damaging effects of many diseases, including infections and some types of cancer. There is no known cure for HIV or AIDS.
HIV and AIDS are part of the same disease, with HIV occurring in the early stages of the disorder and AIDS occurring in the later stages. The HIV virus spreads through a variety of body fluids, including:
There are several strains of HIV. The most common strain is HIV-1, but a person can become infected with more than one strain. Soon after infection, the virus attacks the immune system and begins to multiply in the lymph nodes. HIV also gradually destroys helper T cells (CD4 lymphocytes), the white blood cells that coordinate the immune system.
Eventually, the disease progresses to the point where it becomes classified as AIDS. The Centers for Disease Control and Prevention (CDC) defines AIDS as the presence of HIV infection (having a positive test for the HIV virus) and any one of the following:
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Development of an opportunistic infection. This is an infection that occurs when the immune system is impaired.
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CD4 lymphocyte count of 200 or less. Normal counts range from 600 to 1,000.
Patients infected with HIV are susceptible to various viral, bacterial, fungal and parasitic infections. They are also more likely to develop certain cancers, including:
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Kaposi’s sarcoma. A type of cancer that starts with purplish spots on the feet and legs and spreads from the skin to lymph nodes and internal organs.
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Lymphoma. Malignant (cancerous) tumors that arise in the lymph nodes or in other lymphoid tissue.
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Cervical cancer. Cancer of the cervix, the narrow lower end of the uterus.
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