Acquired immunodeficiency syndrome (AIDS) is the final stage of a viral infection that weakens the immune system and makes the individual susceptible to a host of diseases and cancer which may result in death if not treated.
The disease is caused by human immunodeficiency virus (HIV).
These small viruses have an RNA genome, and once it infects a human cell, it uses a special enzyme called restriction endonuclease that reproduces within the cell. HIV is called as ‘retrovirus’ as it turns RNA into DNA unlike the normal cells where DNA is converted into RNA.
As the virus reproduce, it produces a large number of mutations, resulting in copies which are slightly different from each other. This enables the virus to evade the body’s immunologic defenses and helps to maintaining a life-long infection. This is the reason why it is difficult to develop an effective vaccine against these viruses. Mutations also allow viruses to develop resistance against diseases.