"Cluster 5", also referred to as ΔFVI-spike by the Danish State Serum Institute (SSI), is a variant of SARS-CoV-2, the virus that causes COVID-19, that is believed to be extinct. It was discovered in North Jutland, Denmark, and is believed to have been spread from minks to humans via mink farms. On 4 November 2020, it was announced that the mink population in Denmark would be culled to prevent the possible spread of this mutation and reduce the risk of new mutations happening. A lockdown and travel restrictions were introduced in seven municipalities of North Jutland to prevent the mutation from spreading, which could compromise national or international responses to the COVID-19 pandemic.