Virology is a science which deals with the smallest organism of the world and action played with all the creative. the specially of this organisms is to select all creative as host having no own house. moreover, this organism is globally under stood because of its distributor nature and life expoilage (Eg. Human being, animal and bacteria). in plant kingdom it causes considered damage to several crops including economics crop very significantly. subject virology has widest during last decades but there is no any book where in a systematic approach have been follows in documenting the facts which may serve the purpose of the students as per the university grant commission syllabus. the present book is benign written for the purpose to provide all information about viruses, its effect with hosts as per the syllabus of UGC (university grants commission)deans committee report in view of its effects on human being, animal, plants and other creatures after selecting the host. the effort have been made to write this book which may be very easy to understand by the student of under graduate and post graduate level, as several illustration have been given for its better understanding. the special effort have been made done in stating several disease of human beings, animal and plant kingdom with their economic importance to popularize among the readers. this book precautionary measure have been followed to elaborate the aspects separately with DNA and RNA with contrast to diseases caused in several creatures. Keeping in mind the teaching requirement and demand of literature it was describe to update all document through this book so as to provide recent information of the advanced made in the field of virology. The contents of this book are widely divided for easy understanding of readers.