David Letterman's current sick leave, for shingles, is starting to rival his only previous leave, for heart surgery three years ago. A doctor for the 55-year-old ''Late Show'' host, who initially anticipated that Letterman would be back to work by March 10, now calls his progress ''week-to-week.'' In the meantime, another round of guest hosts will throw pencils from behind Dave's desk for three nights this week, with college basketball tournament play expected to pre-empt the show on Thursday and Friday.
''Dave is getting better, and he is eager to get back to work, but his full recovery will be evaluated week-to-week,'' Dr. Louis Arrone said in a statment on Friday. Subbing for Letterman, who has been sidelined by his eye infection since Feb. 26, have been guest hosts from Bruce Willis and Regis Philbin the first week to Whoopi Goldberg, Vince Vaughn, and Elvis Costello last week. This week, the Associated Press reports, the guest hosts will be ''Everybody Loves Raymond'''s Brad Garrett on Monday, then old-school comic Tom Dreesen (Frank Sinatra's longtime opening act) on Tuesday, followed by ''Life With Bonnie'' star Bonnie Hunt on Wednesday. Letterman has served as boss to both Garrett and Hunt; his company, Worldwide Pants, produces ''Raymond'' and produced Hunt's '90s sitcoms, ''The Building'' and ''The Bonnie Hunt Show.''