Trainer Paul Nicholls has revealed neither Kauto Star nor Big Buck's have been affected by the coughing bug that has hit his yard.
Nicholls cancelled a media day, scheduled for Wednesday, due to the bug that has struck a number of his horses.
The champion trainer is currently preparing for the Cheltenham Festival and Nicholls originally declined to name which of his horses had been hit by the illness.
However, writing in his Betfair column the Somerset trainer revealed that both Kauto Star and Big Buck's had not been struck by the illness.
"In case you're wondering whether Kauto Star, Big Buck's, Join Together or Al Ferof have been affected, they haven't and are all in good form," Nicholls wrote.
Nicholls also moved to ease fears over his other horses who are set for Cheltenham, with the festival set to begin on March 13.
He added: "The horses who have come with back dirty noses and coughs will get antibiotics. Depending on the horse it can be three to five days before they are back in full training. It's much like when we get a head cold - the whole thing goes as quickly as it comes."
Kauto Star has already established himself as a Cheltenham great, with Gold Cup wins in 2007 and 2009, and is set to compete in the showpiece event next month, while Big Buck's heads into the festival bidding for an astonishing fourth consecutive World Hurdle title.