The number of probable cases of the H1N1 flu, or swine flu, at Carson Middle School in the North Allegheny School District has gone up from two cases to five, and three probable cases have been reported in the district's Hosack Elementary School.

The Allegheny County Health Department reported yesterday that the cases are all considered mild illnesses not requiring hospitalization.

"The students are recovering at home and will stay there until they are no longer infectious," said department spokesman Dave Zazac. Some family members have been treated with antiviral medications to protect them against illness, he said. No cases were among siblings.

The Health Department is not recommending the closing of any schools at this time. Sick students, faculty and staff at North Allegheny are encouraged to stay home.

"Absentee rates at Carson and Hosack are somewhat elevated but not nearly high enough to warrant cancellation of classes," said County Health Director Dr. Bruce W. Dixon. The rate is currently typical for a flu season, which is about 10 percent, Mr. Zazac said.

"In fact, the higher absentee rate is a good sign," Dr. Dixon said, "because it's an indication that parents may be heeding our advice to keep their children out of school if they have a fever and other flu-like symptoms. Keeping them at home is the right thing to do and prevents the virus from spreading."

After showing symptoms and seeing the doctor, it is recommended that patients stay home for at least seven days after the onset of symptoms. If symptoms last longer, they are asked to stay home until they are free of symptoms for 24 hours.

The symptoms for parents and caregivers to watch for include a fever of more than 100 degrees, sore throat, cough, congestion, runny nose and extreme fatigue.

It is especially important for high-risk groups, such as the elderly and people with chronic illnesses, to see a doctor about their flu symptoms, Mr. Zazac said. He said circumstances that would lead to a recommendation to close a school might include a flu outbreak in a school with high-risk children, extremely high absenteeism (possibly a rate of 30 to 50 percent), or changes in the virulence of H1N1, which might lead to more severe illness.