SARS-CoV-2 transmission between mink (Neovison vison) and humans, Denmark

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SARS-CoV-2 transmission between mink (Neovison vison) and humans, Denmark

Published 22 March 2021

Hammer, A.S. et al (2021) SARS-CoV-2 transmission between mink (Neovison vison) and humans, Denmark. Emerging infectious diseases, 27 (2), pp. 547-551.

This paper reports on the epidemiological investigation into SARS-CoV-2 infection at three mink farms in the Northern Jutland region of Denmark, to analyse the transmission of virus in mink and the local human community.

Swab samples (blood and throat, nasal, and faecal swabs) were collected from adult mink and kits from 3 different mink farms. Air and feed samples were also collected. Samples were assessed for viral RNA by quantitative reverse transcription PCR (qRT-PCR) and SARS-CoV-2 Ab ELISA.

At initial sampling, seroprevalence was high on farm 1 (>95%) and farm 3 (66%) but, only 3% on farm 2. However, at follow up sampling seroprevalence on farm 2 had increased to >95%.

The authors note that despite the high level of virus detected in the mink there was little clinical disease or increase in death rate, making it difficult to detect the spread of infection; thus, mink farms could represent a serious, unrecognized animal reservoir for SARS-CoV-2.

Air samples from farm 1 tested negative. However, on farms 2 and 3, multiple samples collected from exhaled air from mink or within 1 m of the cages were positive. None of the air samples collected outside the houses were positive. Feed samples collected at each farm tested negative.

SARS-CoV-2–positive samples were then sequenced. The viruses found on farms 1–3 were very similar and these sequences and those from humans linked to the infected farms grouped within the European 20B clade of the global SARS-CoV-2 tree.

The authors conclude that a likely scenario for the spread of infection in mink in Denmark is that the index human case-patient introduced infection into farm 1, where a mutation occurred that could be linked to subsequent human cases. It seems that the variant viruses on farm 1 spread to >1 human and were then transmitted, presumably by human–human contact, to other people and to farms 2 and 3.

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