SARS-CoV-2 bioaerosol transmission in experimentally infected American mink

Abstract

The SARS-CoV-2 BA.1 (Omicron) variant, which emerged in late 2021, is more transmissible than earlier variants but causes milder symptoms in humans. Mink farms, where animals are housed in close quarters, present a high risk for virus transmission and mutation, necessitating strict control measures due to documented cases of mink-to-human and human-to-mink transmission. Hence, we aimed to detect infectious airborne SARS-CoV-2 using BioSampler-air collectors and to investigate aerosol transmission between groups of American mink (Neovison vison). Two groups (male and female) were infected with the BA.1 variant, and samples were collected from aerosols, saliva, feces, and surfaces. The results indicated that infectious viruses were predominantly detected in aerosol samples over a three-day period in both groups. Surface, saliva, and fecal samples also showed potential for virus transmission. Notably, infectious viruses were cultivated from aerosol samples, confirming aerosol transmission among American mink. This study highlights the importance of immediate sample culturing to improve infectious virus detection and emphasizes the need for enhanced preventive measures on mink farms to mitigate the spread of viruses.

Fig. 1

Experimental setup for male (A) and female (B) groups in the BSL3 facility. Metal bar enclosures were placed 10–20 cm apart on a table and the BioSamplers were placed 30 cm from the enclosures, at the height of the animals, to collect air samples from the area surrounding the mink. The samplers’ inlets were faced towards the table the enclosures were on. Inoculated animals are marked with virus illustrations and naïve recipients are as indicated in the figure. Figure created in Biorender (https://BioRender.com).

Fig. 2

Positive cell culture and PCR findings. Infectious isolates represent cultivated virus samples, while viral RNA represents all viruses, infectious and inactive. The thickness of the graph describes the relative number of SARS-CoV-2 positive samples on each day post infection (dpi). Individual positive samples are represented with dots on the graphs. Positive sample medians are illustrated with full lines and quartiles with dashed lines. Negative or weakly positive samplesare not shown in the graph, but they are presented with all other sample data in Supplement Table 1, and 2. On day four, 10 surfaces were sampled instead of four (Supplement Table 1, and 2). Graphs created with GraphPad Prism 10.2.1.