Cryptic transmission of SARS-CoV-2 and the first COVID-19 wave

• Type of Material: Article
• Authors: Jessica T Davis, Northeastern University; Matteo Chinazzi, Northeastern University; Nicola Perra, Northeastern University; Kunpeng Mu, Northeastern University; Ana Pastore Piontti, Northeastern University; Marco Ajelli, Indiana University; Natalie Dean, Emory University; Corrado Gioannini, ISI Foundation; Maria Litvinova, Indiana University; Stefano Merler, Bruno Kessler Foundation; Luca Rossi, ISI Foundation; Kaiyuan Sun, National Institutes of Health; Xinyue Xiong, Northeastern University; Ira M Jr, Longini, University of Florida; Elizabeth Halloran, Fred Hutchinson Cancer Research Center; Cécile Viboud, National Institutes of Health; Alessandro Vespignani, Northeastern University
• Language: English
• Date: 2021-10-25
• Publisher: NATURE PORTFOLIO
• Publication Version: Final Published Version
• Copyright Statement: © The Author(s) 2021
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1038/s41586-021-04130-w
• Title of Journal or Parent Work: NATURE
• Volume: 600
• Issue: 7887
• Start Page: 127
• End Page: +
• Grant/Funding Information: A.V., M.E.H., N.E.D. and I.M.L. acknowledge support from the award NIH-R56AI148284. S.M. acknowledges support from the EU H2020 MOOD project. C.G. and L.R. acknowledge support from the EU H2020 Icarus project. M.A., M.C. and A.V. acknowledge support from the COVID Supplement CDC-HHS-6U01IP001137-01. M.C. and A.V. acknowledge support from the Google Cloud Research Credits programme to fund this project. A.V. acknowledges support from the McGovern Foundation and the Chleck Foundation. The findings and conclusions in this study are those of the authors and do not necessarily represent the official position of the funding agencies, the National Institutes of Health or the US Department of Health and Human Services.
• Keywords: DYNAMICS; EUROPE; Science & Technology; SPREAD; Multidisciplinary Sciences; Science & Technology - Other Topics; EPIDEMIC
• Research Categories: Biology, Biostatistics; Health Sciences, Oncology

Abstract

Considerable uncertainty surrounds the timeline of introductions and onsets of local transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) globally1–7. 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 screening10, 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.