Classification of Viruses and Phylogenetic Relationships

The taxonomy of viruses represents a unique classification system that recognizes boundaries among at first sight a continuum of properties. Genome sequencing has brought into sharp debate the origin of viruses, with RNA viruses perhaps having a separate evolutionary lineage. The criteria adopted for assessing the causal linkage between virus and disease deviates from those normally adopted for bacterial diseases and reflects those unique properties that underlie the principles of virus classification.