AIDS is acquired immuno deficiency syndrome. It is a fatal disease caused by a rapidly mutate retrovirus which attacks the immune system and leaves the patient susceptible to infections, malignancies, and neurological disorders. It was first recognized as a disease in 1981. The virus was isolated in 1983 and was ultimately named the human immunodeficiency virus (HIV). There are two forms of the HIV virus, HIV-1 and HIV-2. The majority of cases worldwide are caused by HIV-1.



It is transmitted primarily by exposure to contaminated body fluids, especially blood and semen. In 1999 an international team of genetic scientists reported that HIV-1 can be traced to a closely related strain of virus, called simian immunodeficiency virus (SIV), that infects a subspecies of chimpanzee (Pan troglodytes troglodytes) in Africa. Chimpanzees are hunted for meat in this region, and it is believed the virus may have passed from the blood of chimpanzees into humans through superficial wounds, probably in the early 1930s.

In a process, HIV infects the CD4 cells of the body's immune system, cells that are necessary to activate B- lymphocytes and induce the production of antibodies. This is still imperfectly understood. The body fights back producing billions of lymphocytes daily to fight the billions of copies of the virus. The immune system is eventually plagued and the body is left vulnerable to opportunistic infections and malignancy.

Some people develop flu like symptoms shortly after infection, but many have no symptoms. It may be a few months or many years before serious symptoms develop in adults; symptoms usually develop within the first two years of life in infants infected in the womb or at birth. Before serious symptoms occur, an infected person may experience fever, weight loss, diarrhea, fatigue, skin rashes, shingles thrush, or memory problems. Infants may fail to develop normally.

The definition of AIDS has been refined, as more knowledge has become available. In general it refers to that period in the infection when the CD4 count goes below 200 from a normal count of 1,000 or when the characteristic opportunistic infections and cancers appear. The conditions associated with AIDS include malignancies such as Kaposi's sarcoma, non-Hodgkin's lymphoma, primary lymphoma of the brain, and invasive carcinoma of the cervix.

Opportunistic infections characteristic of or more virulent in AIDS include Pneumocystis carinii pneumonia, herpes simplex, cytomegalo virus, and diarrhea diseases caused by cryptosporidium or isospora. In addition, hepatitis C is prevalent in intravenous drug users and hemophiliacs with AIDS, and an estimated 4 to 5 million people who have tuberculosis are coinfected with HIV, each disease hastening the progression of the other.

Children may experience more serious forms of common childhood ailments such as tonsillitis and conjunctivitis. These infections conspire to cause a wide range of symptoms like coughing, diarrhea, fever and night sweats, and headaches and may lead to extreme weight loss, blindness, hallucinations, and dementia before death occurs.

HIV is not transmitted by casual contact. Transmission requires a direct exchange of body fluids, such as blood or blood products, breast milk, semen, or vaginal secretions, most commonly as a result of sexual activity or the sharing of needles among drug users. Such a transmission may also occur from mother to baby during pregnancy or at birth. Saliva, tears, urine, feces, and sweat do not appear to transmit the virus.