Bay of Plenty school rolls are being struck by a range of illnesses - including a "nasty virus" that left one school with dozens of absences.
Aquinas College principal Matt Dalton said about 40 Year 12 and 13 students had been off sick this week with a "nasty virus".
This was a blow to the school's attendance, which had been around 95 per cent this term, he said.
He said one student had a diagnosis of influenza and there had been a range of symptoms including diarrhoea, vomiting, sore throats and a cough.
He said fortunately, no teachers were off sick.
The school had been good at following rules around keeping safe around Covid, like mask-wearing and maintaining distance, which helped with the high attendance this term, he said.
Rotorua's Sunset Primary School principal Eden Chapman said two staff and about 20 per cent of students were off sick on Friday.
He said while the school had not had any influenza cases yet, there had been an increase in gastro and a range of other "little illnesses" which may not have previously resulted in kids staying at home.
He said there were a lot of illnesses around, with resulting absences, and he pointed to the messaging around people staying at home if unwell as a big factor.
He said the Omicron outbreak impacted the psyche of the school community regarding sending children in when they were unwell.
Chapman said there were also examples of parents wanting to keep their kids at home, and "all they have to say is the child has a bit of a sniffle".
He said two staff were battling long-Covid as well, which he was concerned about.
Chapman said there was not much the school could do other than offer support and ensure the families had everything they needed.
Western Bay of Plenty Principals Association president and Tauriko School principal, Suzanne Billington, said a steady number of staff and students were off sick with either the flu, Covid-19 or a tummy bug that was going around.
She said winter always saw more people off with the flu, and there were slightly more away from school as there was Covid in the community.
As Covid and the flu came in waves, she said students were unable to work while at home, and having sick staff was the bigger issue as school and class programmes were disrupted.
Rotorua Primary School principal Fred Whata said between 40 and 50 students from the roll of 370 had been away every day this week due to a range of illnesses.
This included Covid and gastro, and had been more pronounced with the change in weather and passed on easily in the school environment.
He said the school was fortunate the teachers have not fallen ill so far.
While the school was well-equipped in digital learning, he said it was also important for those who are unwell to rest and recover properly.
John Paul College acting principal Maree Stewart said a tummy bug had affected some students and staff over the past two weeks.
She said symptoms included vomiting and diarrhoea. However, the illness was typically only lasting about 24 hours.
She said these gastro-like illnesses tended to "spread relatively quickly, but also go relatively quickly" in the school environment. Some teachers requested that students wore masks during class time this term, which she thought could help curb the spread.
"Students are very respectful of this, we are very lucky."
Meanwhile, there were "very reduced numbers" of Covid cases within the school community - with only four students reporting cases to the school this week.
Tahatai Coast School principal Matt Skilton said the rate of student absences was up by about 10 per cent at present.
A gastro bug had hit the school in week two of this term, however, Skilton said the number of students and staff reporting vomiting and nausea symptoms was now subsiding.
"We have had a little bit of an influx the past couple of weeks. The second week of term was our biggest hit - not so much now," he said.
"You get a wave of these things coming through every year, and this one was particularly swift and quick."
Daily thorough cleaning of surfaces and shared resources within the school was helping minimise the spread of illnesses, he said.
"You just fall back on those systems - it's being diligent on the light switches, tabletops and the shared resourcing. It makes a huge difference."
Lakes District Health Board paediatric head of department Dr Sonja Crone said it was seeing the effects of the change of seasons, a drop in temperature and the opening of international borders with a rise in respiratory tract infections - including bronchiolitis and asthma - in its area.
"The trend is that it's increasing and we're concerned as there are signs that we are in for a bad winter."
Crone said given the drop in childhood immunisation rates there was also concern about the potential for the spread of measles this winter.
"Mask wearing, good hand hygiene and ensuring childhood immunisations are up to date will really help to reduce the likelihood of children and vulnerable people needing hospital level care."
The Bay of Plenty District Health Board said it was not aware of any gastro circulating in schools. However, it said these bugs were "always present" in the community.
Toi Te Ora Public Health medical officer of health Dr Phil Shoemack said there had only been nine confirmed cases of influenza in the Bay so far this year.
Of those cases, five were hospitalised. But Shoemack said an increase in infections was expected over winter.