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. 2020 Aug 20;182(4):812–827.e19. doi: 10.1016/j.cell.2020.06.043

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This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

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Figure S2 — The Increasing Frequency of the D614G Variant over Time in North America, Related to Figure 1

Maps of the relative frequencies of D614 and G614 in North America in two different time windows. B. Weekly running counts of G614 illustrating the timing of its spread in North America. This figure complements Figures 2 and S3, and Figure 1 has details about how to read these figures. When a particular stay-at-home order date was known for a state or county it is shown as a pink line, followed by a light pink block indicating the maximum two-week incubation time. Different counties in California had different stay-at-home order dates (Mar. 16-19) so are not highlighted, but more detail can be seen regarding California in Figure S4. The decline in D614 frequency often continues well after the stay-at-home orders were initiated, and sometimes beyond the 14-day maximum incubation period, when serial reintroduction of the G614 would be unlikely. On the right, Washington State is shown, with details from two heavily sampled counties, Snohomish and King. Both counties had well-established ongoing D614 epidemics when G614 variants were introduced, undoubtedly by travelers. Washington state’s stay-at-home order was initiated March 24. At this time there were 1170 confirmed cases in King County, and 614 confirmed cases in Snohomish County. (Confirmed COVID19 case count data from: COVID-19 Data Repository by the Center for Systems Science and Engineering (CSSE) at Johns Hopkins University). Testing was limited, and so this is lower bound on actual cases. Of the sequences sampled by March 24, 95% from King County (153/161) and 100% from Snohomish County (33/33) were the original D614 form (Part B, details at https://cov.lanl.gov/). By mid-April, D614 was rarely sampled. Whatever the geographic origin of the G614 variants that entered these counties, and whether one or if multiple G614 variants were introduced, the rapid expansion of G614 variants occurred in the framework of well-established local D614 variant epidemics. Santa Clara county is one of the two exceptions to the pattern of D614 decline in Figure 1B: details are provided in Figures S4A and S4C.