Mayor Michael Bloomberg said that four students and an assistant principal who is critically ill have documented cases of swine flu at a Queens middle school. More than 50 students have gone home sick with flulike symptoms there, he said.
At another middle school in Queens, 241 students were absent Thursday. Dozens more were sick at an elementary school.
Bloomberg said that three locations - all special education schools with more than 4,000 students - would be closed for at least a week because "there are an unusually high level of flulike illnesses at those schools."
"There are documented cases of H1N1 flu at one of them," the mayor said, using the formal name for swine flu.
The mayor said that the sick assistant principal may have had pre-existing health problems. In many other swine flu cases that turned critical, patients had pre-existing conditions.
New York City's first known cases of swine flu appeared in late April, when hundreds of teenagers at a Roman Catholic high school in Queens began falling ill following the return of several students from vacations in Mexico, where the outbreak began.
At first, the virus appeared to be moving at breakneck speed. An estimated 1,000 students, their relatives and staff at the St. Francis Preparatory School fell ill in a matter of days.
City health officials became aware of the outbreak on April 24. The school closed and health officials began bracing for more illnesses throughout the city.
But the outbreak then seemed to subside. Additional sporadic cases continued to be diagnosed, but the symptoms were nearly all mild. The sick children recovered in short order. St. Francis reopened after being closed for a week.
The middle school with the confirmed cases is two miles from St. Francis.
Health officials in New York and elsewhere said that the virus, at least in the U.S., appeared to pack no more serious a punch than the seasonal influenza viruses that arrive each winter.
In other H1N1 news, A woman in Arizona suffering from a lung condition has apparently become the fourth person with swine flu in the nation to die, authorities said Thursday.
The Maricopa County Health Department reported that the woman in her late 40s died last week of what appears to be complications of the new strain of influenza.
Laboratory tests confirmed that the woman was infected with the flu strain. The federal Centers for Disease Control and Prevention is expected to add her to the official national tally on Friday, health department spokeswoman Jeanene Fowler said.