A Study on some Stochastic Models for Estimation of Expected time

It is a historical fact that the sporadic outbreak of the epidemics such as plague, cholera and small-pox used to claim a great toll of human lives all over the world during the first half of the twentieth century. But in the later decades of the twentieth century, the whole world witnessed a pandemic situation with the advent of the dreadful and disastrous disease called Acquired Immuno Deficiency Syndrome (AIDS) caused by the Human Immuno deficiency Virus (HIV). This pandemic disease, HIV/AIDS is entirely different from the endemic like malaria and the epidemic diseases mentioned above, and it is caused by bacteria, viruses, fungi, parasites and other organisms. HIV the pathogenic micro organism which is a lentivirus attacks the immune system in the human body as all other viruses of this type do. It is unfortunate that there is no remedy or cure for this HIV; and the effects of the scientists (to invent a remedy for this) had to face only defiant result.