Michael Worobey and colleagues analyzed collections of SARS-CoV-2 genomes from around the world to decipher their viral family trees and to determine whether introductions of the virus in early January 2020 in Washington State and in Germany led to major outbreaks in the U.S. and Europe. In the U.S., their reconstruction of events suggests that the first confirmed U.S. case in Washington State in early January prepared the local and state response so that state officials were relatively successful initially in slowing the virus' spread, compared to places like New York City. However, an influx of returning travelers in late January or early February, who were only loosely monitored by public health officials, may have led to multiple introductions of the virus that sparked community spread in Washington State and California, the researchers say. Worobey et al. also took a closer look at the first confirmed SARS-CoV-2 in Europe, and whether this late January case in Bavaria, Germany, might be have sparked Italy's major outbreak in Lombardy in February. They conclude that the Bavarian virus variant is unlikely to be the cause of the northern Italy outbreak. While genomic data have suggested differences in the timing, spatial origins and transmission dynamics of early SARS-CoV-2 outbreaks, particularly in the U.S., Worobey and colleagues say their findings emphasize that epidemiological linkages inferred from genetically similar SARS-CoV-2 associated with outbreaks in different locations can be "highly tenuous," given low levels of sampled viral genetic diversity and insufficient background data from key locations. They say their findings highlight the potential value of establishing intensive, community-level respiratory virus surveillance architectures, such as the Seattle Flu Study, during a pre-pandemic period.
Trevor Bedford, Alexander L Greninger, Pavitra Roychoudhury, Lea M Starita, Michael Famulare, Meei-Li Huang, Arun Nalla, Gregory Pepper, Adam Reinhardt, Hong Xie, Lasata Shrestha, Truong N Nguyen, Amanda Adler, Elisabeth Brandstetter, Shari Cho, Danielle Giroux, Peter D Han, Kairsten Fay, Chris D Frazar, Misja Ilcisin, Kirsten Lacombe, Jover Lee, Anahita Kiavand, Matthew Richardson, Thomas R Sibley, Melissa Truong, Caitlin R Wolf, Deborah A Nickerson, Mark J Rieder, Janet A Englund, The Seattle Flu Study Investigators, James Hadfield, Emma B Hodcroft, John Huddleston, Louise H Moncla, Nicola F Müller, Richard A Neher, Xianding Deng, Wei Gu, Scot Federman, Charles Chiu, Jeff S Duchin, Romesh Gautom, Geoff Melly, Brian Hiatt, Philip Dykema, Scott Lindquist, Krista Queen, Ying Tao, Anna Uehara, Suxiang Tong, Duncan MacCannell, Gregory L Armstrong, Geoffrey S Baird, Helen Y Chu, Jay Shendure, Keith R Jerome.
Cryptic transmission of SARS-CoV-2 in Washington state.
Science, 2020. doi: 10.1126/science.abc0523