Common symptoms were fevers, aches and pains and generally "feeling miserable", she said.
The second illness moving through the community in recent weeks was gastric, with symptoms lasting a couple of days.
Kokatahi-Kowhitirangi School principal Megan McLellan said yesterday the ratio of unwell students was the highest she had seen in her 12 years of teaching.
Forty one students out of 60 were away yesterday, and 38 the day before.
"It is far worse than we had when swine flu was around and there was all the fuss in the media," she said.
"I can't recall any time in my teaching career having this number of students away. They've had fevers and a long run of being unwell so its not just an easy flu."
Staff have been encouraging families to keep children away until completely better to stop the spread.
Unfortunately, for rural families it was a bad time for sickness to strike being calving season, Mrs McLellan said.
At Kaniere School up to 30 children were away on any one day last week.
Secretary Ann Jones said that number had halved as of yesterday, with 15 children off school.
However, that was still an increase, with normally only one or two students absent a day.
"It has abated a bit this week but it seems to be moving through the classrooms," Mrs Jones said.
There were still students "going down with it" with symptoms lasting anywhere up to five days.
Hokitika Primary School reported it had felt the affects for about three weeks. At the height up to 60 children were away, from 150.
It was now down to about 20, a spokeswoman said yesterday.
At Westland High School the middle school appeared to be the worst affected. Deputy principal Linda Hutt said this week only 54 per cent of year 9 and 58 per cent of year 10 students had been in class.
Attendance for Year 8s was about 70 per cent. A number of staff had also been struck.
They too were trying to manage the situation by appealing to families to keep any students with symptoms at home.
Dr Dyzel also recommended flu immunisations.
Last month the Ministry of Health extended the 2015 seasonal influenza immunisation programme to the end of August.
It said at the time the winter flu season was yet to peak in New Zealand.
The vaccine is free for people aged 65 and over, pregnant women, people with long term health conditions such as severe asthma, and children under 5 who have been hospitalised for a respiratory illness. It is also available to buy from general practices and many pharmacies for those not eligible for the free injection.
- Hokitika Guardian