Auckland has had its worst week for flu hospitalisations in a decade.

There were 177 people admitted to the four Auckland hospitals with severe acute respiratory illness (SARI) from the 9 August to 16 August, up from 125 patients the week before.

PHF Science said the past weeks hospitalisation rate is the highest weekly hospitalisation rate for Tāmaki Makaurau since 2015.

Dr Hannah Cooper, a public health physician in the health intelligence team at PHF Science, said while it was not a worse flu than usual, there was more of it around.

"Last Thursday there'd been a real sort of spike in activity, but it was still kind of within the sort of normal range for the peak of a season.

"This week it really has increased further.

"It's a particularly severe week of winter illness, which I think really corroborates what's being reported from all the frontline health services about how busy they are."

Dr Cooper said the severe acute respiratory illness is surveillance based off "flu-like illnesses" presenting at Auckland hospitals.

"We use that as a kind of snapshot of what's probably happening across the country."

However it doesn't paint a full picture.

"The thing that it requires, is having a fever... And while fever is really common as part of a flu-like illness, some people can have the flu or RSV or Covid and actually not have a fever."

They are not counted in this number, so the number of people sick with a flu-like illnesses could be higher.

"What's different this winter is that there's still a lot of other respiratory illness around. There's a lot of RSV, a lot of rhinovirus.

"So in the background of already quite a lot of winter illness and then this big spike in flu, the combination of those two things has tipped us into this very, very high level of respiratory illness putting a lot of pressure on the health system."

PHF Science data showed calls to Healthline also increased and were higher than at this time in 2023, 2024, and 2025.

The majority of the calls to Healthline came from the Central region.

Some hospitals in that region, such as Palmerston North, have had patients report waiting more than 17 hours to be seen in ED.

Zero to four year olds, followed by people aged 65-plus are the two groups with the highest number of hospitalisations, while babies and toddlers were also the most common age group admitted to ICU in 2026 with respiratory illness.

The data showed that a variety of Influenza A - H3N2 was the most prevalent in the community.

Dr Cooper said that was also known as the "Subclade K strain" which caused a bad outbreak in Europe earlier this year.

"Subclade K sort of got its own name because it was quite different, it had evolved quite a lot from recent other influenza AH3 viruses.

"And the more that a flu virus evolves, the less our bodies are able to sort of remember it from previous flu seasons."

She said that meant there was probably not a lot of natural immunity in the community and that was why it was running through the population.

"But the good news is that our vaccine was updated ahead of the season in the southern hemisphere to match the Subclade K and our labs testing to date shows that the strains circulating are a good match for the vaccine.

"While this caused a really bad flu season in Europe in terms of absolute numbers, there's a lot of flu, there wasn't any sign that it caused more severe flu in people that got it."

New data from Health New Zealand showed another nearly 6000 people have been vaccinated against the flu in the past week.

There were 5328 vaccinated in early August and 7076 the week before that.