When strains are evolving at 1 to 10 nucleotides per year per genome, it is important to address as much of the genome sequence information as possible within the limits of what can be achieved accurately. This cannot be 100% of the genome with current sequencing technologies. For example, regions that are repeatedly present in the genome either identically or with minor variations (for example the ribosomal RNA sequences) are inherently difficult to address. Exactly how much