Quasispecies and molecular evolution of viruses

Ribonucleic acid (RNA) viruses evolve as complex distributions of genetical ly different but closely related variants termed viral quasispecies. The pr ecise genome of a quasispecies cannot be defined, since the consensus genom e is an average of many variants. The dynamics of quasispecies ha's conside rable implications for the understanding of the adaptability and pathogenic potential of viruses, and in addition, for the design of preventive and th erapeutic measures for the diseases caused by these viruses. The authors su mmarise current knowledge on the structure of quasispecies, and the biologi cal implications of this structure.