The winter flu has hit Rotorua hard with 200 students from one high school absent for one day this week.
The absences at Rotorua Boys' High School made up nearly a quarter of its 870 students on its roll.
The school's hostel has also battled swine flu with students being forced to be isolated from their roommates after swine flu was diagnosed in four students.
The students, who have  recovered, are among 27 Rotorua people diagnosed with swine flu so far this winter.
The school is unable to determine how many of the other 200 absences are for swine flu.
Toi Te Ora Public Health medical officer of health Dr Neil de Wet said the Rotorua numbers for swine flu were "the tip of the iceberg" and in no way identified the wider number of people who had been struck.
 
Dr de Wet said they only received notification of people who had been confirmed with the diagnosis through lab testing.
"Not everyone will go to their doctor and not everyone who goes to the doctor gets swabbed," he said.
"There are specific clinical guidelines for when it's important to swab."
He said these included patients admitted to hospital to ensure they were treated correctly.
He said the numbers so far were in line with what was happening nationally and they expected to hear of more cases as winter progressed.
"We're not seeing any specific patterns, it's throughout the community," Dr de Wet said.
"We were involved with managing the cases at Rotorua Boys' High School's hostel. There were only a handful of cases and they were placed in a separate flat."
These boys are all now back in class and their roommates and friends were given a course of Tamiflu as a precaution, school principal Chris Grinter said.
Other students had called in sick but because they were under the care of their own family doctor he did not know how many had influenza-type illness.
"We're comfortable the situation is under control and it's not escalated," he said.
He said the school already offered the influenza vaccine to its staff and would consider offering it to students who stayed in the hostel next year.
The number of students absent was up about 5 per cent based on the same period last year but he said that also included those who were off school for bereavement, holidays or sports fixtures.
On Tuesday 200 of its 870 were absent. It was unknown how many were absent yesterday.
 
Meanwhile other Rotorua high schools are reporting similar absentee rates to previous winters.
At Rotorua Lakes High School on Monday, 25 parents and caregivers called in to report sick students, deputy principal Wayne Hall said. This is from a roll of 600.
 "We've only had two students confirmed with swine flu."
He said they expect an absentee rate of 8 to 10 per cent each winter.
Rotorua Girls' High School principal Annette Joyce said the school's absence roll had been fluctuating the past three weeks due to the car crashes involving its students. She said there appeared to be some sickness about but "I don't know if it's swine flu or not".
"I've even had two days off school and that's unheard of for me."
The Ministry of Health is reminding people that New Zealand is still seeing a significant level of pandemic influenza even though the World Health Organisation has announced the world is now in the post-pandemic phase.