Sark, one of the smallest of the Channel Islands, has its first known case of coronavirus.
The person was already in self-isolation before testing positive for Covid-19 over the weekend, said the States of Guernsey.
The individual, who travelled to Sark, had had no contact with others and posed minimal risk to the island, it added.
It follows 20 cases being found in Alderney at the weekend.
'Kind of inevitable'
The States said in a statement: "The person was a traveller and tested negative on arrival.
"They later developed symptoms while in self-isolation and subsequently tested positive.
"Initial contact tracing has established that the individual has no contacts and no other individuals are being required to self-isolate as a result of this case.
"While the risk of any onward transmission from this case is extremely low, some targeted surveillance testing is taking place, as an additional precaution, to give assurance to Sark's community."
Conseiller John Guille, from Sark Chief Pleas, the government on the island of about 500 people, said the person came over on a cargo boat, so would not have been in contact with tourists, and went into isolation on arrival.
"This was kind of inevitable. The risk is incredibly low for people on Sark," he said.
"We have had hundreds of travellers going into isolation and it is quite surprising it has not happened already."