State health officials say the number of confirmed swine flu cases in New Jersey has nearly doubled since last week and area schools are closing their doors as a result.

The state has confirmed 31 new cases of the H1N1 influenza since late Thursday in 11 of the state's 21 counties. Those include Bergen, Burlington, Camden, Essex, Hudson, Mercer, Monmouth, Morris, Ocean, Passaic and Somerset.

People infected range in age from 8 months to 55 years old.

The infected include three students at Lawrenceville School in Mercer County. County officials say two more are being tested. To minimize the spread of the virus, the school will be giving take-home exams instead of finals and holding its graduation ceremony outside.

Seven confirmed cases have been found at the Thurgood Marshall Elementary School in Asbury Park. The school canceled classes in order to disinfect the premises. Classes will resume Thursday.

There have been no swine flu deaths in New Jersey.

AP wires contributed to this report.