The 25-year-old also pulled out of last week's Shenzhen Open in China with the illness and will be lacking match practice when the Australian Open, the year's first grand slam, begins in Melbourne on Jan. 18.
"I'm really disappointed to have to withdraw ... but unfortunately I am still not feeling well," Kvitova, who has not played a competitive match since the Fed Cup final in November, said in a statement.
"Being defending champion, this tournament obviously means a lot to me and I've always had a wonderful time playing this event.
"I look forward to coming back in future years to play."
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
(Reporting by Greg Stutchbury in Wellington; Editing by Peter Rutherford)
