This has happened at the Belmont Care Home in Stranraer, where new admissions have also been halted.
A total of 10 cases of the virus have been identified at the site.
The care home is operated by the charity St Philips Care, and a spokesperson for the organisation said: “As soon as the outbreak developed, we took immediate action halting visits and implementing a number of additional robust infection control measures including increased testing and an ongoing decontamination schedule.
A spokesperson for Dumfries and Galloway Health and Social Care Partnership said cases are"stubbornly high" in the district and have been identified across the region.
They have reminded anyone with symptoms to isolate and get tested.