Swine flu has taken over from seasonal flu as the main flu type circulating in the country.
Sue Huang, head of the National Influenza Centre at the Wallaceville-based Crown research laboratory ESR, says the change follows the pattern of other southern hemisphere countries, including Australia.
Latest information from the national influenza surveillance network also shows steep increases in the number of people seeing their doctor for flu in Ruapehu, Southland and Hawke's Bay.
Dr Huang says the steep increases in those consulting doctors in Ruapehu, Southland and Hawke's Bay could be linked to skiers visiting two of those areas during the recent school holidays.
She says children and teenagers are the main ones seeing a doctor.
Children under one also dominated hospitalisations, with the highest rates of hospitalisation for flu in Canterbury.
The Minister of Health says the recent school holidays may have offered a brief respite in dealing with swine flu.
Fifteen people have died from swine flu in this country and case numbers are rising steeply in many places.
Health Minister Tony Ryall says it is too soon to tell whether the pandemic is about to reach its peak.