NEW YORK - A school assistant principal who was sick for several days with the H1N1 virus died on Sunday, New York City's first death linked to the virus and the sixth in the U.S.

Mitchell Wiener, who had been hospitalized and on a ventilator, had been sick with the virus for nearly a week before his school was closed on Thursday.

Complications besides the virus likely played a part in his death, Flushing Hospital Medical Center spokesman Andrew Rubin said.

Mayor Michael Bloomberg said the death of Wiener, who was 55 and had taught for decades, "is a loss for our schools and our city."

"He was a well-liked and devoted educator," Bloomberg said in a statement.

Besides Wiener, no one else in New York City has become seriously ill from the virus. As of Sunday afternoon, health officials had reported five other deaths in the U.S.: three in Texas, one in Washington state and one in Arizona.

Most people sickened from the swine flu, or the H1N1 virus, have complained of mild, seasonal flu-like symptoms such as fever, cough, sore throat, body aches and fatigue.

The city's first outbreak of H1N1 virus occurred three weeks ago, when about 700 students and 300 other people associated with a Catholic high school in Queens began falling ill following the return of several students from vacations in Mexico, the epicentre of the outbreak. The school was closed.

Five more city schools were to close Monday because of concern for swine flu, bringing the total to 11, including Wiener's.