Maintenance workers scrubbed desks and door handles Friday in a flu swine outbreak that shut down three New York City public schools and left an assistant principal hospitalized in critical condition on a breathing tube.

Education Department spokeswoman Margie Feinberg said maintenance crews were thoroughly cleaning and disinfecting two middle schools and one elementary school in Queens where hundreds of students were sent home sick this week.

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Mayor Michael Bloomberg announced the school closures Thursday evening, saying four students and the assistant principal at the Susan B. Anthony middle school in Hollis have documented cases of swine flu.

The mayor said the assistant principal, Mitch Wiener, may have had pre-existing health problems — but on Friday, Wiener's son Adam said his father had only suffered previously from gout, which he said was unrelated to his current condition. He said his father is now suffering from kidney failure, pneumonia, dehydration and a lung infection.

"I don't know where people got that," Adam Wiener, 23, said Friday morning as he prepared to return to the hospital where his mother and one brother were holding a vigil.

"The only pre-existing condition he has is gout, which is unrelated to complications he's experienced now."

Adam Wiener said his father had been sick since at least last weekend with flu-like symptoms "but we didn't think anything of it." Then early Wednesday, he said, the family called 911 after his father began "hallucinating and wasn't coherent."

Wiener's case marks the most severe illness in the city since the city's first known cases of swine flu appeared in late April. At least five schools in the city were closed then, but all have since reopened. Officials say the students who have fallen ill in this latest surge of illness appear to be experiencing mild symptoms, similar to routine flu.

Bloomberg said the three schools — with more than 4,000 students altogether — 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.

New York City's first outbreak occurred 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.

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 and St. Francis reopened after being closed for a week.

The middle school with the confirmed cases is two miles from St. Francis.

People at the Susan B. Anthony school said students started going home sick on Tuesday and Wednesday, alarming parents.

"I'm worried," said Dino Dilchande, whose sixth-grade son goes to the school. "The city should have taken more precautions. We should have been notified earlier."

Administrators posted a sign on the door from the Health Department informing students and teachers that the school would be closed for a week. The school is in the Hollis section of Queens, a neighborhood known for producing several rappers including the group Run-DMC.

At the start of the flu outbreak in the United States, government health officials recommended that schools shut down for two weeks if there were students with swine flu. But when the virus turned out to be milder than initially feared, the Centers for Disease Control and Prevention dropped that advice but urged parents to keep children with flu symptoms home for a week.

So far, the virus has not proved to be more infectious or deadly than the seasonal flu.

CDC officials said schools may decide to close if there is a cluster that's affecting attendance and staffing.

Adam Wiener said his father has been mostly unconscious because of sedation since Wednesday evening, breathing with the help of a ventilator.

One of Wiener's 18-year-old twin sons, Jordan, said his father had been awake briefly and asked him about his leg, which he had injured playing baseball.

"He's always about his kids first," Jordan Wiener said Friday. "He was asking me how I was feeling and how my season's going."