More than 100 people are thought to have been struck down by a vomiting and diarrhoea bug at a luxury hotel.
NHS Tayside said it was investigating suspected cases of norovirus at Gleneagles Hotel in Auchterarder, Perth and Kinross.
It said more than 100 people connected to the five-star resort had reported symptoms of the illness over the last week.
Environmental health officers from Perth and Kinross Council and NHS Tayside's health protection team are investigating.
The health board said: "Staff at the hotel are working closely with NHS Tayside and Perth and Kinross Council to implement all the recommended infection control measures.
"As always, anyone suffering from similar symptoms should be very careful with their hand hygiene and should remain at home until 48 hours after their symptoms have cleared up.
"If people are concerned about their health they should contact their own GP or NHS 24 on 08454 242424 in the out-of-hours period."
The hotel is home to Scotland's only two-star Michelin star restaurant, Andrew Fairlie at Gleneagles, and it hosted the international G8 summit in 2005.
A spokeswoman for Gleneagles said: "We can confirm there have been a number of reported cases of norovirus last weekend. All the relevant authorities were notified and we have been working in conjunction with them to assess the situation on an ongoing basis during the week.
"The care of our guests and staff is of paramount importance and we have been taking the necessary precautions. We are glad to say that as far as we are aware, only a handful of people have not yet returned to full health."