According to the Zurich Christmas Open website, Viktor Korchnoi had to cancel his participation in the tournament due to health reasons. Here's the Google Translate version:
Unfortunately, Viktor Korchnoi can not fulfill his wish of participating in the traditional tournament. Health reasons force him to stay at home. We wish him a speedy recovery and all the best in the coming year.
For those of you looking to get your fix of old-timey chess players, Anatoly Karpov and Jan Timman are playing a four-game rapid (40' + 30") match. Game 1 was played earlier today and was drawn in a fairly dull game, thanks to Karpov's unfortunate but understandable continued advocacy of the Scandinavian with 3...Qd8.