The huge surge in ambulance 111 calls is abating, but Hato Hone St John says it is still extremely busy as the winter flu peak stretches into spring.

The service was treating many people in respiratory distress or with other complications of flu-like illness, and putting back-office staff into ambulance crews to fill gaps.

A month ago St John declared a major incident, saying it had hit record call numbers, and patients with non life threatening conditions could wait hours.

Director of ambulance operations Doug Gallagher said it was then getting about 17,000 calls a week.

That was now 15,000 a week, but still well above the roughly 13,000 they would expect to see in a busy winter, he said.

The late surge in influenza and other respiratory illnesses had taken the service by surprise after a mild start to the season.

"We thought we'd gone off lightly and then bang, all of a sudden we saw the 111 call volumes and incidents go through the roof and off the chart levels we've never seen before," he said.

"We saw 111 call volumes and incident volumes higher than we saw during Covid, higher than we typically see during New Year's Eve."

Much of the current pressure was being exacerbated by St John staff sickness, he said.

The service was continuing to take workers from its support teams and put them into on the frontline, if they had the right qualifications, he said.

There was still challenges in offloading patients at hospitals, with ambulance officers often having to wait with them because there was not a bed in the emergency department.

Gallagher said there had been progress in improving drop-off though, including some officers able to look after two patients if it was safe to.

The seriousness of calls St John received varied greatly, with some people very sick, and others looking for advice about whether an ambulance was needed, for example, he said.

Statistics from PHF Science last week showed the flu hospitalisations were continuing to rise, with the country's youngest children by far the most affected.