On 2020-02-21 a superspreading event most likely occurred in Washington. 6 days later (2020-02-27) it started to super-spread through the community. A total of 81 copies of this genome (that represents the core of the outbreak), were reported in Gisaid, a proxy for primary transmissions, along with 270 genomes that are one-step mutation with respect to the core genome (a proxy for secondary transmissions). The signature for the likely superspreading event ends at about 2020-03-07, 15 days after it started, with 4061 sequences found in total.
The last sequence of the superspreading event was collected on 2020-06-16.