Life Science

I . Introduction

In 1981 , a cluster of cases of Pneumocytis pneumonia appeared in the Los Angeles area . This extremely rare disease was usually seen only in persons who were immunosuppressed . Investigators soon correlated the appearance of this disease with an unusual incidence of a rare form of cancer of the skin and blood vessels called Kaposi 's sarcoma . The people affected were all young homosexual men , and all showed loss of immune function . By 1983 , the pathogen causing the loss of immune function had been identified as a retrovirus that selectively infects

certain T cells . This virus is now known as human immunodeficiency virus (HIV HYPERLINK "http /www .questia .com /SM .qst ?act adv contributors Richard 20C 20Stroh man dcontributors Richard 20C 20Strohman " Strohman , 2003

There have been several theories about the origin of HIV . It is now believed that it arose by mutation of a virus that had been endemic in some areas of central Africa for many years . The virus has been found in blood samples preserved from as early as 1959 in several African nations and in England

Thesis Statement : This investigates why HIV is such a successful pathogen and other details that an individual should know about HIV

II . Literature Review

A . Opportunistic Organisms

Although it is convenient to categorize symbiotic relationship by type we must keep in mind that under certain conditions the relationship can change . For example , given proper circumstances , a mutualistic organism such as E . coli , can become harmful . E . coli is...