Germs have struck again! Is no cultural institution safe? While the Met is hemorrhaging singers due to illness, the New York Philharmonic's conductor, Riccardo Muti, has been forced off the dais this week by the flu. He will be replaced by Michael Christie. During his first time conducting the orchestra, he will be leading works by Elgar and Copland on Thursday at 7:30 p.m., Friday at 11 a.m. and Saturday at 8 p.m. Fortunately for Mr. Christie, he doesn't have far to travel. He is music director of the Brooklyn Philharmonic. Just be sure to load up on Vitamin C, Mike!