I.S. 318 in Williamsburg shut its doors Friday afternoon after more than 50 students either missed class or came to school with flu-like symptoms, according to the city health department.

The principal of I.S. 318 says a custodian has already disinfected the classrooms. The principal also says he sent a letter home to parents Friday stating concerns that the absences were related to the city's flu outbreak.

Five schools in Queens were closed Friday, including J.H.S. 74 and P.S. 107. The P.S. 107 that's closed is the school in Queens, not the one in Brooklyn.

The assistant principal at one of the Queens schools, Mitch Wiener, of I.S. 238, is in critical condition with a confirmed case of the H1N1 virus. He's suffering from pneumonia, kidney failure, dehydration and a lung infection.

An inmate at Rikers Island was also identified as a confirmed case of swine flu Friday. A spokesperson for the Department of Corrections says the man's condition is not serious and no other prisoners at the Bronx facility have contracted the virus.

Swine Flu Information