Fig. 1: The emergence and rapid geographic expansion of Delta.
From: Context-specific emergence and growth of the SARS-CoV-2 Delta variant
a, Time-calibrated phylogenetic reconstruction of Delta based on 1,000 sequences subsampled from 93,649 sequences from 100 countries (52,992 from England). The tree was split into three subtrees (with n = 28,783, 28,715 and 36,151 sequences, respectively) prior to full analysis. The roots of these three subtrees, and of lineage AY.4 are labelled with black squares. Lineage colours represent the inferred countries and/or regions where transmission occurred. b, The number of sequenced cases of Delta per week in India, England and globally, where ‘global’ refers all countries other than England and India. c, The proportion of sequenced, reported positive cases in India and England (solid lines, n = 52,992 sequences from England, corresponding to 84% of all sequences from the UK during the study period) and the proportion of sequenced cases classified as Delta in India and England (dashed lines).
