NEW YORK - Mayor Bloomberg is set to announce how the city plans to handle flu season as the new school year approaches.The mayor will hold a briefing Tuesday afternoon to discuss how the city will be prepared for a possible swine flu outbreak. Last year, schools around the city closed due to swine flu and officials estimated about 800,000 New Yorkers caught the virus. Gov. David Paterson began a series of town hall meetings Monday about swine flu.