Acquired Immunodeficiency Syndrome (AIDS) is a disease caused by Human Immunodeficiency Virus (HIV).
The AIDS pandemic is a major concern in both developed and developing countries. The World Health Organization estimates that the cumulative number of AIDS cases in the world amounted to 2.5 million persons. AIDS, the Acquired Immunodeficiency Syndrome is not a hereditary disease but is caused by HIV (Human Immunodeficiency Virus).
HIV from an infected person can pass to a normal person through blood contact generally during unprotected sex with infected persons and sharing needles or syringes contaminated with small quantities of blood from HIV positive person.
HIV can also pass from infected mothers to their babies during pregnancy, delivery or breast feeding. HIV does not spread through tears, sweat, urine, faces or saliva during Normal kissing. It does not spread by sharing utensils, towels, clothing, and toilet seats or insects bite like that of mosquito or bed bug.
AIDS was discovered in 1983. Most evidence has suggested that AIDS spread from Africa. It is believed that the virus has been transferred to humans from primates like Africa monkey or Chimpanzees.
Important features of AIDS
1. A person, which is HIV positive, carries the HIV in his body. The virus damages the immune system.
2. With time, the immune system becomes very weak.
3- Symptoms of AIDs include persistent cough, generalized pruritic dermatitis, or pharyngeal candidacies, chronic progressive and disseminated Herpes simplex and generalized lymphadenopathy, recurrent Herpes Zoster, weight loss, chronic diarrhoea and prolonged fever.
4. Nobody knows exactly when with HIV will become sick of AIDS.
5. Human Immunodeficiency Virus is transmitted through semen and vaginal fluids.
The virus and course of infection
The main cellular target of HIV is a special group of white blood cells critical to the immune system which is known as helper T lymphocytes, or helper T cells. Helper T cells play a key role is normal immune responses by producing factors that activate almost all immune cells.
HIV is a retrovirus, the genetic material of which consists of RNA (not DNA) surrounded by a lipoprotein envelope. HIV cannot multiply on its own and instead relies on the machinery of the host cell to produce new viral particles. Once the virus has infected a T cell, HIV copies its RNA into a double stranded DNA copy by means of viral enzyme reverse transcriptase.
Because the reverse transcriptase lacks the ‘proof reading’ function that most DNA synthesizing enzymes have, many mutations may arise as the virus replicates, further hindering the ability of the immune system to combat virus.
The viral genome copied on DNA transcript is integrated into host cell DNA. This integration may occur at any accessible site in the host genome and results in permanent acquisition of the viral genes by the host cell the course of HIV infection involves three stages: primary HIV infection, the asymptomatic phase, and AIDS.
During the first stage, the transmitted HIV replicates rapidly, and some persons may experience an acute flu-like illness that persists for one or two weeks. During this time a variety of symptoms may occur, such as fever, enlarged lymph nodes, sore throats, muscles and joint pain, rash and malaise.
The second phase of HIV infection, the asymptomatic period, lasts an average of 8-12 years. During this period, which is symptomless phase, the virus continues to replicate, there is a slow decrease in the number of helper T cells.
When the helper T cell count falls to about 200 cells per micro liter of blood, patients begin to experience opportunistic infection, i.e., infections that arise only in individuals with a defective immune system. This is AIDS, the final stage of HIV infection.