Advances in molecular biology have led to huge increases in determining the phylogenetic history of viruses. This book is one of the first solely devoted to the origins and evolution of viruses, and of the ways in which they interact with their cellular hosts and vectors. Intitial chapters cover impacts of viruses and their control. Further chapters detail genetic variation of viruses and the molecular basis of interrelation at the population level and the molecular basis and evolution of this relationship. Seventeen chapters follow on genetic origins, sources of variation, population genetics, and interactions with hosts. Practical virologists will find the chapters on phylogenetic analysis techniques very useful. The highly adaptive nature of viruses will be of particular interest to evolutionists.