On 2020-12-09 a superspreading event most likely occurred in California. 11 days later (2020-12-20) it started to super-spread through the community. A total of 30 copies of this genome (that represents the core of the outbreak), were reported in Gisaid, a proxy for primary transmissions, along with 26 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 2020-12-24, 15 days after it started, with 6374 sequences found in total.
The last sequence of the superspreading event was collected on 2021-01-14.