Knowledge of the nucleotide sequence of a viral genome enables the design of specific oligonucleotides for use as primers for selective amplification of a target nucleic acid from a pool of complex template by a polymerase chain reaction (PCR) driven by Taq , a thermostable DNA polymerase (1 ,2 ). The amplified fragment can be analyzed by gel electrophoresis for its presence or characterized by nucleic acid hybridization and restriction enzyme digestion for its heterogeneity.