There also appears to be a difference in the strains. The NYC strain seems to mostly come from the European branch, while the CA infection comes directly from

There also appears to be a difference in the strains. The NYC strain seems to mostly come from the European branch, while the CA infection comes directly from China (and likely much earlier in 2020). There appears to be some difference in virulence between the strains. https://www.medrxiv.org/content/10.1101/2020.04.08.20056929v2 https://www.medrxiv.org/content/10.1101/2020.04.08.20056929v... and https://nextstrain.org/ncov/global https://nextstrain.org/ncov/global