No further information about the 70-year-old conductor's condition was available.
Ozawa will be replaced by Peter Schneider, a frequent guest conductor at the opera house. Schneider, the company noted, led Idomeneo in Vienna in 1997 and has been rehearsing the opera at the Bavarian State Opera in Munich.
The production, which runs January 27-February 16, has also lost its director, the noted German opera and stage director Willy Decker, to illness. Karin Voykowitsch, Decker's assistant, will oversee the production in his stead.