NHS Orkney is “profoundly concerned” coronavirus is spreading rapidly across the islands after nine people were linked to new cases.
The health board has reported no confirmed Covid cases since June 15.
However, chief executive Michael Dickson has said he knows of a “significant number” of positive tests, some of which can be attributed to mainland health board figures as the patient’s home address is registered elsewhere.
Mr Dickson said people had travelled to homes in the isles and the mainland after developing symptoms.
He told The Orcadian newspaper a minimum of nine people were involved in this emerging situation, and that they were connected to a single workplace.
Mr Dickson explained among these nine people, a number have already tested positive.
He also said it is understood that there may have been some contact between this group and other members of the community, and contact tracers are currently working to identify anyone who may have come into contact with them.
He told the newspaper: “If we can control this situation, we can avoid a situation like Aberdeen.
“I don’t think we are facing a cluster like that, but we need to do the right things and help protect ourselves and our loved ones.”
A statement from NHS Orkney read: “NHS Orkney is responding to a significant Covid public health issue and we are profoundly concerned that the virus is spreading rapidly across our community.
“We believe there is a real risk to the people of Orkney, including those on the remote isles, and urge them to take care.
“Several individuals have developed Covid symptoms and then travelled to their homes across the isles and to mainland Scotland.
“NHS Orkney is taking this matter extremely seriously and working with partners, which include several NHS mainland boards, port authorities, ferry operators, environmental health and the Orkney Island Council.
“We will keep the public informed as to the number of positive cases confirmed on island regardless of their home address.”
Anyone who develops symptoms on the island has been urged to self-isolate immediately, while track and trace teams are working to find the contacts of confirmed cases.