Investigation of a superspreading event preceding the largest meat processing plant-related SARS-Coronavirus 2 outbreak in Germany

Abstract

Background Here, we describe a multifactorial investigation of the events of a SARS-CoV-2 outbreak in the largest meat processing complex in Germany. Methods Timing of infection events, spatial relationship between workers in the meat processing plant, climate and ventilation conditions, sharing of living quarters and transport, and full viral genome sequences recovered from PCR-confirmed SARS-CoV-2 cases were analyzed. Findings Transmissions occurred in a confined area of a meat processing plant in which air is constantly re-circulated and cooled to 10°C. Index case B1 transmitted the virus to co-workers in a radius of more than 8 meters during work-shifts on 3 consecutive days. Assessment of viral sequences shows that all cases share a set of eight single nucleotide mutations representing a novel sub-branch in the SARS-CoV-2 C20 clade. We identified the same set of mutations in samples collected in the time period between the initial infection cluster and a subsequent outbreak in the following month, with the largest number of confirmed SARS-CoV-2 positive cases in a meat processing facility reported so far. Interpretation Our results indicate climate conditions and airflow as factors that can promote efficient spread of SARS-CoV-2 via distances of more than 8 meters and provide insights into possible requirements for pandemic mitigation strategies in industrial workplace settings. Funding None.