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More About HIV/AIDS
HIV (human immunodeficiency virus) is a virus that causes the progressive destruction of the human body's immune system, eventually resulting in the condition called AIDS (acquired immunodeficiency syndrome). It is the sixth leading cause of death for people aged 25-44 in the United States.
By gradually destroying the body's immune system, HIV makes it harder for individuals to fight off diseases. Parasites, bacteria, yeasts, and viruses that commonly do not cause serious disease in people with normal immune systems can cause fatal illnesses in people with AIDS.
HIV has been found in:
- nervous system tissue, spinal fluid, blood
- Pre-seminal fluid (the liquid that comes out before ejaculation)
- vaginal fluid
- breast milk
There are two types of HIV, but in the United States "HIV" refers to HIV-1 unless otherwise stated. HIV-1 and HIV-2 both destroy immune cells called CD4+ T cells. These blood cells are important in the body's fight against diseases. When the CD4+ T cells are below 200 cells per cubic millimeter, then the infection has progressed to AIDS.
HIV-2 is a second type of HIV that was discovered in 1986. It has the same modes of transmission as HIV-1 and the same association with AIDS. However, it progresses more slowly in its early development and progresses faster as the disease advances. HIV-2 is mostly found in Africa.
HIV is classified as a retrovirus. This class of viruses contains those that use RNA (ribonucleic acid) as their genetic material. HIV infects a cell and then uses an enzyme called reverse transcriptase to change its RNA into DNA (deoxyribonucleic acid). The virus then replicates itself using the machinery of the victim cell.
There are similar kinds of HIV viruses that target nonhuman species. Examples of these include the feline immunodeficiency virus (FIV) that affects cats and the simian immunodeficiency virus (SIV) that affects monkeys and other primates. These viruses help scientists research the virus, although they are not exactly the same as HIV.