On 2020-06-23 a superspreading event most likely occurred in Japan. 25 days later (2020-07-18) it started to super-spread through the community. A total of 220 copies of this genome (that represents the core of the outbreak), were reported in Gisaid, a proxy for primary transmissions, along with 536 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 2020-08-08, 46 days after it started, with 6658 sequences found in total.
The last sequence of the superspreading event was collected on 2020-09-04.