Occupational and environmental exposure to SARS-CoV-2 in and around infected mink farms

Abstract

Uncontrolled SARS-CoV-2 infections in farmed minks raised concerns regarding environmental transmission of SARS-CoV-2 from minks to farm workers and the general population living in the vicinity of infected farms. We aimed to assess occupational and environmental exposure by intensive environmental investigations in and around infected Dutch mink farms. Air sampling was performed in farms, at farm premises and at nearby residential sites. A range of other environmental samples were collected from minks’ housing units including bedding material. SARS-CoV-2 RNA was analyzed in all samples by qPCR. Inside the farms, considerable levels of SARS-CoV-2 RNA were found in airborne dust especially in personal inhalable dust samples (~1,000-10,000 copies/m3). Most of the settling dust samples scored positive for SARS-CoV-2 RNA, 82% (75/92). SARS-CoV-2 RNA was not detected in outdoor air samples, except for those collected near the entrance of the most recently infected farm. Many samples of the minks’ housing units and surfaces contained SARS-CoV-2 RNA. To conclude, infected mink farms can be highly contaminated with SARS-CoV-2 RNA. This warns for occupational exposure which was substantiated by considerable SARS-CoV-2 RNA concentrations in personal air samples. Dispersion to outdoor air was found to be limited and SARS-CoV-2 RNA was not detected in air samples collected beyond farm premises, implying a negligible environmental exposure risk for nearby communities. Our occupational and environmental risk assessment is in line with whole genome sequencing analyses showing mink-to-human transmission in farm workers, but no indications for direct zoonotic transmission events to nearby communities.