Acquired Immune Deficiency Syndrome (AIDS) is caused by Human Immune deficiency Virus (HIV). AIDS was first recognized in the United States in the summer of 1981. Centers for Disease Control and Prevention (CDC) Atlanta, USA, reported the unexplained occurrence of Pneumocystis jiroveci (formerly Pneumocystis carinii) pneumonia in five previously healthy homosexual men in Los Angeles. Infection of Pneumocystis jiroveci is an opportunistic infection that can infect humans only when body immunity is low and can not infect normal persons. The disease became recognized in male and female injection drug users (IDUs) and soon thereafter in recipients of blood transfusions and in hemophiliacs within months. It became clear that an infectious agent transmissible by sexual (homosexual and heterosexual) contact and blood or blood products was the most likely culprit of the epidemic.
In 1983, human immunodeficiency virus (HIV) was isolated. In 1984 it was demonstrated clearly to be the causative agent of AIDS. In 1985, a sensitive enzyme-linked immunosorbent assay (ELISA) was developed for testing HIV/AIDS. The epidemic in USA has now become pandemic (throughout the world).
The causative agent of AIDS is HIV. It belongs to the family of human retroviruses (Retroviridae) and the subfamily of lentiviruses. Lentiviruses cause disease in other animal species, including sheep, horses, goats, cattle, cats, and monkeys. The four recognized human retroviruses belong to two distinct groups: the human T lymphotropic viruses (HTLV)-I and HTLV-II, which are transforming retroviruses; and the human immunodeficiency viruses, HIV-1 and HIV-2. The most common cause of HIV disease throughout the world is HIV-1. HIV-1 has several subtypes with different geographic distributions. HIV-2 was first found in West Africa and confined to that area, but recently it has been traced to sexual contacts with West Africa in other parts of the world. The Pan troglodytes troglodytes species of chimpanzees has been established as the natural reservoir of HIV-1 and the most likely source of original human infection. HIV-2 is also found among animals. First human contact of HIV most likely contacted from the above named chimpanzee species.
The definition of HIV/AIDS is given by CDC is based on CD4+T lymphocyte count and clinical condition. This is based on three ranges of CD4+T lymphocyte count and three clinical categories, a total of nine categories. So by the above definition if a person has CD4+T cell count of less than 200 per micro liter of blood than the person is having AIDS regardless of symptoms or opportunistic infection. If a patient has a clinical symptom of category B, he can not be reverted back to category A, even he no more have the symptom. The same is true to category C patients also, once they are classified as category C, they can not be reverted back to category B or A.
The following table gives detail about the classification of HIV/AIDS patient. PGL stands for progressive generalized lymphadenopathy.
|
CD4+T Cell Count |
A Asymptomatic, Acute HIV or PGL |
B Symptomatic, Non A or C Condition |
C AIDS-Indicator Conditions |
|
>500/micro liter |
A1 |
B1 |
C1 |
|
200–499/micro liter |
A2 |
B2 |
C2 |
|
<200/micro liter |
A3 |
B3 |
C3 |
By the above chart/table it is easier to classify a HIV/AIDS patient.
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