English: Each set of circles along a line segment represents a molecular sequence from an individual infection. Circles are coloured to differentiate sequences. (top) Under one-to-one subtyping, every unique sequence represents a different subtype. This strategy is more common single-locus typing or pathogens with a relatively slow rate of evolution, which limits the variation that accumulates over time. (bottom) With cluster-based subtyping, multiple sequences are assigned to the same subtype. This strategy is favoured under multi-locus or whole-genome sequencing or rapidly evolving pathogens, where every sampled infection may have a unique sequence.