Health officials say 4,700 cases could be linked to the Boardmasters festival, which was recently held in Newquay
The Cornish tourist board has urged people not to visit unless they have pre-booked and to test themselves extensively after a sharp rise in cases in the county.
The chief executive of Visit Cornwall, Malcolm Bell, said visitors should aim to “treble their efforts as much as possible” with the hands, face, space guidance and try to remain outdoors.
