It may be substantially less expensive, on the order of 3-fold, to generate draft compared with finished sequence data for an organism like Marburg virus, according to estimates using Equation 1. For example, for $45K, one could sequence either two finished genomes or one finished and three draft. However, draft sequencing of this low quality (3· to 6·) for Marburg causes a dramatic decline in the ability to computationally eliminate regions of poor conservation, and thus to exclude poor signature regions ( Figure 2 ). This occurs because gaps in the draft data of some of the sequences mask sequence variation among strains. Using the best available data, all six finished genomes, there is 75.2% sequence conservation. The deficiencies of draft data give a false impression that there is 92.6% sequence conservation (Table 1) . Each additional finished genome reduces the conserved fraction by $5%, compared with a reduction of only 2% per genome for the draft data.