A nagging viral infection has forced tenor Ben Heppner, seen with Soprano Deborah Voigt in 2005, to withdraw from the Canadian Opera Company's 60th anniversary concert. (Julie Jacobson/Associated Press)

A nagging illness has forced renowned Canadian tenor Ben Heppner to withdraw from the Canadian Opera Company's upcoming 60th anniversary concert, for which he was considered among the major highlights.

The COC made the announcement over the weekend, with the concert slated for Nov. 7.

Heppner caught the bug during a recent October engagement at the Royal Opera House, where he was singing Tristan in a Covent Garden production of Tristan und Isolde.

"I caught an infection in London and I had hoped to have fully recovered by this time," Heppner said in a statement.

"Unfortunately, a visit with my doctor and my coach confirmed that I will not be able to give the first-class performance Toronto audiences deserve."

Organizers announced, however, they have secured a pair of Heppner's high-profile, fellow Metropolitan Opera colleagues to fill in: Canadian baritone Russell Braun and Mexican tenor Ramon Vargas. Late Monday, the COC also added British tenor John Treleaven, renowned for his Wagnerian roles, to the lineup.

"We are terribly sad that Ben is unable to perform with us on Saturday. His presence means a lot … and we're sorry that he can't be here to celebrate with us," said COC general director Alexander Neef.

"I am very happy that we have secured some great vocal talent to celebrate the COC's 60th anniversary and Johannes Debus's first appearance as new music director. We know that this new program, along with the wonderful COC Orchestra, will make for a spectacular concert."