Accurate understanding of the global spread of emerging viruses is critical for public health responses and for anticipating and preventing future outbreaks. Here we elucidate when, where, and how the earliest sustained severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission networks became established in Europe and North America. Our results suggest that rapid early interventions successfully prevented early introductions of the virus from taking hold in Germany and the United States. Other, later introductions of the virus from China to both Italy and Washington state, United States, founded the earliest sustained European and North America transmission networks. Our analyses demonstrate the effectiveness of public health measures in preventing onward transmission and show that intensive testing and contact tracing could have prevented SARS-CoV-2 outbreaks from becoming established in these regions.


All data used in this analysis are free to access: a BEAST .xml file example, FAVITES simulated phylogenies, the GISAID accession numbers for all sequences used in the analysis, and alignments are hosted at GitHub (https://github.com/Worobeylab/SC2_outbreak) and Zenodo (26). The GISAID data are also provided in table S3. This work is licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0) license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. To view a copy of this license, visit https://creativecommons.org/licenses/by/4.0/. This license does not apply to figures/photos/artwork or other content included in the article that is credited to a third party; obtain authorization from the rights holder before using such material.

Cite as

Worobey, M., Pekar, J., Larsen, B., Nelson, M., Hill, V., Joy, J., Rambaut, A., Suchard, M., Wertheim, J. & Lemey, P. 2020, 'The emergence of SARS-CoV-2 in Europe and North America', Science, 370(6516), pp. 564-570. https://doi.org/10.1126/science.abc8169

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Last updated: 29 October 2022
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