‘Triple burden’ of respiratory diseases driving early surge into hospitals

The latest ESR data showed hospitalisations with severe acute respiratory illness (SARI) in Auckland crossed the seasonal baseline in late March, when 54 cases were reported within a week. Herald Illustration / Guy Body

A trio of respiratory nasties is driving spikes in hospital cases weeks ahead of the sick season’s typical start – prompting calls for Kiwis to book their flu vaccinations.

The latest ESR data showed hospitalisations with severe acute respiratory illness (SARI) in Auckland crossed the seasonal baseline in late March when 54 cases were reported within a week.

Those rates were tracking roughly in line with last year when flu season kicked off unusually early - both years notably higher than the same time in 2022.

ESR public health physician Dr Sarah Jefferies said there wasn’t one driver behind the trend, but a “triple burden” of respiratory ills.

“We’re seeing Covid, influenza, RSV [respiratory syncytial virus] - and also the common cold virus, rhinovirus - among those patients that have more severe illness.”

Across the Tasman, New South Wales health authorities reported nearly 10,000 confirmed influenza cases so far this year – up 60 per cent on the same time last year - along with increased RSV and Covid-19 activity.

While flu was still circulating at generally low levels in New Zealand, Jefferies said most of the major strains had already been detected here over recent weeks.

Those recently sampled were predominantly A/H1N1 or “swine flu” - known to hit elderly people and young children particularly hard.

When H1N1 and influenza B swept back into New Zealand in 2023 after a years-long absence, the result was an abnormally drawn-out flu season.

“If [H1N1] is the predominant strain, it’s very possible that we might see higher trends in young kids,” Jefferies said.

“Of course, there’s also RSV, which for under two-year-olds is a virus that can cause particularly severe illness – so we’ll have to wait and see what happens.”

An early spike in severe cases of respiratory illness has been observed in Auckland ahead of the normal flu season. Photo / Jason Oxenham

She said H1N1 was among the strains targeted by this year’s flu vaccine, now freely available to people over 65 and other higher-risk groups.

“As we’ve been seeing these early surges in illness, it’s a really good reminder for people to plan to get their seasonal influenza vaccines.”

In a normal year, the flu killed around 500 Kiwis - making it our single deadliest infectious disease - before Covid-19 emerged in New Zealand.

Otago University epidemiologist Professor Michael Baker expected the coronavirus would again claim more lives than flu in 2024 – although the toll could be slightly lower than the more than 1300 deaths reported last year.

“We are finding that mortality is about 50 per cent higher following Covid than it is with influenza - but both have long tails of negative effects,” he said.

“Covid is also infecting a lot more people every year than influenza - and it’s clearly much more of a multi-system disease.”

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.