On 2020-03-12 a superspreading event most likely occurred in Michigan. 1 days later (2020-03-13) it started to super-spread through the community. A total of 244 copies of this genome (that represents the core of the outbreak), were reported in Gisaid, a proxy for primary transmissions, along with 162 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 2020-03-28, 16 days after it started, with 1188 sequences found in total.
The last sequence of the superspreading event was collected on 2020-04-24.