The number of confirmed cases in the country rose from 18 on Friday to 183 on Sunday, reflecting both the speed at which the variant has spread and the sensitivity of Denmark’s virus surveillance system.

The northern European country is a leader in the sequencing of variants, acting as an early-warning system for the continent. The rise in confirmed omicron cases there could be an indication that the variant has spread more widely throughout Europe than previously known.

Before the Danish data was released Sunday, the European Center for Disease Prevention and Control reported just 182 cases of omicron across all of the European Union, plus Norway and Iceland.