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

Here, we describe a multifactorial investigation of the events of a SARS-CoV-2 outbreak in the largest meat processing complex in Germany. 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. 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. 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 this initial infection cluster and a subsequent outbreak within the same factory with the largest number of confirmed SARS-CoV-2 positive cases in a meat processing facility reported so far. Our results indicate climate conditions, fresh air exchange rates, and airflow as factors that can promote efficient spread of SARS-CoV-2 via long distances and provide insights into possible requirements for pandemic mitigation strategies in industrial workplace settings.