https://www.sciencedaily.com/releases/2020/06/200630111456.htm

The data comes from Our World in Data ( https://ourworldindata.org/about), a project of the Global Change Data Lab, a registered charity in England and Wales. This organization collected information from the European Centre for Disease Prevention and Control for cumulative daily case counts and deaths for 208 countries over a period of 122 days from Dec. 31, 2019, to April 30, 2020. The investigators analyzed the data with a variation of a statistical technique known as a cluster analysis.

In this approach, data points are grouped according to similarity. The countries form clusters as individual outbreaks become more similar.