Distinct patterns of SARS-CoV-2 transmission in two nearby communities in Wisconsin, USA

• Authors: Michael Martin, Emory University; Katia Koelle, Emory University; Gage K. Moreno, University of Wisconsin Madison; Katarina M. Braun, University of Wisconsin Madison; Kasen K. Riemersma, University of Wisconsin Madison; Peter J. Halfmann, University of Wisconsin Madison; Chelsea M. Crooks, University of Wisconsin Madison; Trent Prall, University of Wisconsin Madison; David Baker, University of Wisconsin Madison; John J. Baczenas, University of Wisconsin Madison; Anna S. Heffron, University of Wisconsin Madison; Mitchell Ramuta, University of Wisconsin Madison; Manjeet Khubbar, City of Milwaukee Health Department Laboratory; Andrea M. Weiler, University of Wisconsin Madison; Molly A. Accola, University of Wisconsin School of Medicine and Public Health; William M. Rehrauer, City of Milwaukee Health Department Laboratory; Shelby L. O'Connor, University of Wisconsin Madison; Nasia Safdar, University of Wisconsin School of Medicine and Public Health; Caitlin S. Pepperell, University of Wisconsin School of Medicine and Public Health; Trivikram Dasu, City of Milwaukee Health Department Laboratory; Sanjib Bhattacharyya, City of Milwaukee Health Department Laboratory; Yoshihiro Kawaoka, University of Wisconsin Madison; David H. O'Connor, University of Wisconsin Madison; Thomas C. Friedrich, University of Wisconsin Madison
• Journal Title: medRxiv
• Publisher: NIH | 2020-07-10
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1101/2020.07.09.20149104
• Subjects: Health Sciences, Epidemiology; Health Sciences, Medicine and Surgery; Health Sciences, Immunology
• Keywords: SARS-CoV-2; SARS-CoV-2, COVID-19 infection; viral suppression; genomics

Abstract

Evidence-based public health approaches that minimize the introduction and spread of new SARS-CoV-2 transmission clusters are urgently needed in the United States and other countries struggling with expanding epidemics. Here we analyze 247 full-genome SARS-CoV-2 sequences from two nearby communities in Wisconsin, USA, and find surprisingly distinct patterns of viral spread. Dane County had the 12th known introduction of SARS-CoV-2 in the United States, but this did not lead to descendant community spread. Instead, the Dane County outbreak was seeded by multiple later introductions, followed by limited community spread. In contrast, relatively few introductions in Milwaukee County led to extensive community spread. We present evidence for reduced viral spread in both counties, and limited viral transmission between counties, following the statewide Safer-at-Home public health order, which went into effect 25 March 2020. Our results suggest that early containment efforts suppressed the spread of SARS-CoV-2 within Wisconsin.