Emergence of a New Lineage 1C Variant of Porcine Reproductive and Respiratory Syndrome Virus 2 in the United States

Mariana Kikuti, Igor Paploski, Nakarin Pamornchainavakul, Catalina Picasso-Risso, Mark Schwartz, Paul Yeske, Brad Leuwerke, Laura Bruner, Deborah Murray, Brian D. Roggow, Pete Thomas, Lori Feldmann, Matthew W Allerson, Melissa Hensch, Tyler Bauman, Brent Sexton, Albert Rovira, Kimberly VanderWaal, Cesar A. Corzo

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18 Scopus citations


We report an ongoing regional outbreak of an emerging porcine reproductive and respiratory syndrome virus (PRRSV2) variant within Lineage 1C affecting 154 breeding and grow-finishing sites in the Midwestern U.S. Transmission seemed to have occurred in two waves, with the first peak of weekly cases occurring between October and December 2020 and the second starting in April 2021. Most of cases occurred within a 120 km radius. Both orf5 and whole genome sequencing results suggest that this represents the emergence of a new variant within Lineage 1C distinct from what has been previously circulating. A case-control study was conducted with 50 cases (sites affected with the newly emerged variant) and 58 controls (sites affected with other PRRSV variants) between October and December 2020. Sites that had a market vehicle that was not exclusive to the production system had 0.04 times the odds of being a case than a control. A spatial cluster (81.42 km radius) with 1.68 times higher the number of cases than controls was found. The average finishing mortality within the first 4 weeks after detection was higher amongst cases (4.50%) than controls (0.01%). The transmission of a highly similar virus between different farms carrying on trough spring rises concerns for the next high transmission season of PRRS.

Original languageEnglish (US)
Article number752938
JournalFrontiers in Veterinary Science
StatePublished - Oct 18 2021

Bibliographical note

Funding Information:
The authors would like to thank MSHMP participating pig production systems and swine practitioners for their willingness to share information, as well as the collaborating Veterinary Diagnostic Laboratories from UMN, ISU, SDSU, and KSU.

Funding Information:
This project was funded by the Swine Health Information Center (SHIC, www.swinehealth.org), Project # 19-235 SHIC (CC, MK, and CP-R), University of Minnesota Swine Disease Eradication Center - PRRS 144 Whole Genome Sequence Study (CC, MK, and NP) and the joint NIFA-NSF-NIH Ecology and Evolution of Infectious Disease (www.nsf.gov), award 2019-67015-29918 (KV, IP, and NP). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Publisher Copyright:
© Copyright © 2021 Kikuti, Paploski, Pamornchainavakul, Picasso-Risso, Schwartz, Yeske, Leuwerke, Bruner, Murray, Roggow, Thomas, Feldmann, Allerson, Hensch, Bauman, Sexton, Rovira, VanderWaal and Corzo.


  • disease outbreak
  • epidemics
  • epidemiology
  • porcine reproductive and respiratory disease virus
  • swine diseases


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