Pathogenesis

Virus pathogenesis is a complex, variable, and relatively rare state. Like the course of a virus infection, pathogenesis is determined by the balance between host and virus factors. Not all the pathogenic symptoms seen in virus infections are caused directly by the virus but are side effects of the immune response. In the past few decades, molecular genetic analysis has contributed enormously in understanding the virus pathogenesis. In the chapter, three major aspects of virus pathogenesis are considered: direct cell damage resulting from virus replication, damage resulting from immune activation or suppression, and cell transformation caused by viruses. The chapter also discusses the mechanisms of cellular injury, virus-induced immunodeficiency, virus-related diseases, bacteriophages, and cell transformation by viruses, retroviruses, and DNA viruses. The chapter ends with a discussion of new pathogenic viruses that are being discovered all the time, and changes in human activities that have resulted in the emergence of new or previously unrecognized diseases.