The H1N1 virus has been confirmed at three B.C. schools, in an apparent early and aggressive start to the flu season.

The three schools with confirmed H1N1 cases are: Notre Dame Regional Secondary and St. Patrick Regional Secondary in Vancouver, and Shawnigan Lake School on Vancouver Island.

Some schools have seen absenteeism skyrocket in recent days. School officials are required to contact health authorities whenever absenteeism surpasses 10 percent.

At Notre Dame, 70 out of 545 students were absent on Tuesday, though it is uncertain how many of them stayed home because they were sick, said Doug Lauson, superintendent of Catholic Independent Schools of Vancouver.

The school's first dance of the year that was scheduled for Wednesday night has been cancelled.

Elsie Roy Elementary in Vancouver's Yaletown neighbourhood reported that 111 out of 329 students were absent on Tuesday, though there has yet to be confirmation whether any students are ill from H1N1. Six staff members were absent on Wednesday, as well.

At St. Patrick's, absentee rates have been reported to be normal.

Health officials stress that even if H1N1 is the cause for a child's illness, serious cases are rare.

They are asking sick children to stay home until they get better and see a doctor if they have underlying health conditions.