Bloomberg and other city officials were set to announce the multi-pronged strategy later Tuesday to fight a second, more serious wave of the virus that sickened hundreds of thousands, many in schools.
Other elements of the city's plan include tracking influenza at emergency rooms and posting that and other data on a new flu Web site.
The city will also produce a daily report on public school absenteeism and schools reporting five or more cases of flu-like illness.
And the administration plans to send out hundreds of volunteers known as "flu fighters" to visit senior centers, houses of worship, schools and other gathering places to educate New Yorkers about the flu.
Nearby Nassau County is also gearing up for the flu season, urging returning students to
The swine flu vaccine, which is not yet available but expected in mid- to-late October, will be optional but offered to both public and private students. The city's public school system is the largest in the U.S., with 1.1 million pupils.
New York City's swine flu outbreak that began in April and killed more than 50 New Yorkers was first detected in a private high school in Queens. Nationwide, it has killed about 500 people.
Government health experts are rushing to prepare for a worst-case scenario that could see up 30 to 50 percent of Americans infected and 90,000 deaths, though Centers for Disease Control and Prevention officials said those predictions were.
Certain groups have shown to be more vulnerable to swine flu, including children and young adults.
"This flu seems to have gone around the world for this summer, which is the winter in the southern hemisphere," Bloomberg said Monday, before his preparedness plan was announced. "It's come back in some other places. Whether it will come back here, nobody knows."
As part of this year's swine flu plan, which was developed over the summer, if a school sees five or more cases of flulike illness in one day, the school will send a letter to parents stressing the need to keep sick children home.
Schools that experience "excessive" flu activity - 4 per cent of the student body on a single day - will get a visit by a doctor or supervising nurse to further assess the situation.
The supervisor will examine the school's infection-control efforts that should already be in place - like restrooms stocked with soap and paper towels - and will also decide whether the Health Department should recommend additional measures, like closing the facility.
The city warned that school closings would be a last resort, as federal officials have said it is angoing into this fall and winter flu season.
Officials said they do not expect swine flu to cause widespread severe illness, but warned that hospital emergency rooms could be overburdened with worried people again this season, similar to what happened last spring.
To prepare for that, the city is identifying other venues to treat flu patients; under this part of the plan, some of the city's health clinics could be designated as flu centers for people to get vaccinations and outpatient care.
And in an emergency, the city said it could treat large numbers of people by deploying volunteers through its Medical Reserve Corps, a network of 8,700 doctors, pharmacists, nurses and other health professionals.