“Coronavirus quickly spread around the world as early as October 2019”
Viruses accumulate mutations in their genomes as they spread from person to person. By comparing the genomes of different SARS-CoV-2 samples collected at different times in different places, and by combining these data with contact tracing data, it is possible to establish the genealogy and mutation rate of SARS-CoV-2, and thereby trace its origin and when and where it spread. Current data indicates that SARS-CoV-2 made its jump from animals to humans sometime during Fall 2019 and had already spread outside of China by January 2020.