Considerable uncertainty surrounds the timeline of introductions and onsets of local transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) globally 1 – 7 . Although a limited number of SARS-CoV-2 introductions were reported in January and February 2020 (refs. 8 , 9 ), the narrowness of the initial testing criteria, combined with a slow growth in testing capacity and porous travel screening 10 , left many countries vulnerable to unmitigated, cryptic transmission. Here we use a global metapopulation epidemic model to provide a mechanistic understanding of the early dispersal of infections and the temporal windows of the introduction of SARS-CoV-2 and onset of local transmission in Europe and the USA. We find that community transmission of SARS-CoV-2 was likely to have been present in several areas of Europe and the USA by January 2020, and estimate that by early March, only 1 to 4 in 100 SARS-CoV-2 infections were detected by surveillance systems. The modelling results highlight international travel as the key driver of the introduction of SARS-CoV-2, with possible introductions and transmission events as early as December 2019 to January 2020. We find a heterogeneous geographic distribution of cumulative infection attack rates by 4 July 2020, ranging from 0.78% to 15.2% across US states and 0.19% to 13.2% in European countries. Our approach complements phylogenetic analyses and other surveillance approaches and provides insights that can be used to design innovative, model-driven surveillance systems that guide enhanced testing and response strategies. Modelling highlights international travel as the main driver of the introduction of SARS-CoV-2 to Europe and the USA, and suggests that introductions and local transmission may have begun in January 2020.
【저자키워드】 SARS-CoV-2, Computational biology and bioinformatics, Mathematics and computing, 【초록키워드】 coronavirus, Europe, SARS-COV-2 infection, Infection, Local, Transmission, complement, severe acute respiratory syndrome Coronavirus, Epidemic, Phylogenetic analysis, Surveillance, attack rate, International, Travel, community transmission, phylogenetic analyses, respiratory, USA, distribution, timeline, SARS-CoV-2 infections, Geographic distribution, dispersal, criteria, attack rates, acute respiratory syndrome, acute respiratory syndrome coronavirus, acute respiratory syndrome coronavirus 2, growth, heterogeneous, cumulative, approach, European, country, event, highlight, initial, reported, can be used, provide, porous, 【제목키워드】 COVID-19, transmission of SARS-CoV-2,