Hospitals, GP clinics still busy with flu: Why has it hit NZ so hard this year?

One of the biggest flu seasons in years is likely to drag on well into spring, doctors say, as hospitals and GP clinics continue to see high case numbers.

And while the worst of the sick season is likely now behind us, people are being urged to get their flu shots if they haven’t yet.

ESR surveillance showed weekly hospitalisations of people with severe acute respiratory illness (Sari) in Auckland are still tracking far higher than the 2015-19 average, as well as rates from the last two years.

At the wave’s peak in late July, there were 125 hospital cases of severe respiratory infections in the region in one week - about a third more than the same time in 2023 - prompting a plea from health agencies for people to get vaccinated and stay home if sick.

Since then, weekly numbers had eased slightly to just over 100, ESR data for mid-August showed.

ESR surveillance showed weekly hospitalisations of people with severe acute respiratory illness (Sari) in Auckland are still tracking far higher than the 2015-19 average, as well as rates from the last two years. Source / ESR

“While rates are now decreasing as we move into late August and early September, we are remaining vigilant,” Health New Zealand - Te Whatu Ora national clinical director Dr Susan Jack said.

Though the data only showed activity in Auckland, Jack said it was a good barometer of illness levels likely being experienced by hospitals across the country.

GP clinics were also still busy dealing with flu cases, Royal New Zealand College of General Practitioners medical director Dr Luke Bradford said.

“Anecdotally, we are still seeing a lot of respiratory presentations across the country, the South Island is particularly hard-hit at present,” he said.

“We expect these illnesses at this time of year, but there does seem to be more influenza around this year than in the last couple.”

There’d also been six serious outbreaks involving respiratory viruses around the country over mid-August, five of them in aged residential care facilities.

National calls to Healthline for flu-like illnesses - mostly involving babies and young children - continued to run higher than the 2015-19 average.

ESR virologist Dr Sue Huang said the busy flu season had been driven by influenza A strains spreading in tandem.

Those were H3N2 and “swine flu” H1N1 - both of which were known to hit elderly people and kids particularly hard.

“They have been circulating side-by-side and peaked only two weeks apart, which contributed to the very high number of flu cases at hospitals.”

Bradford said most cases seen by GPs were also presenting with influenza A, “as this makes them feel very unwell, and they are more likely to get checked by their doctors”.

ESR virologist Dr Sue Huang. Photo / Mark Mitchell

In late January, influenza A happened to be implicated in an outbreak that killed six residents of a Whitianga rest home.

Huang said doctors had meanwhile seen little of influenza B, which swept back into New Zealand last year with H1N1 after a years-long absence.

“That’s the only unknown for us at the moment - whether we’ll see influenza B play up before the end of the season.”

Otherwise, flu rates were expected to keep tracking down into spring.

Going by past post-peak patterns, Bradford anticipated flu levels should drop over the next four weeks, “so we should see levels right down by October”.

Flu wasn’t the only viral nasty keeping clinics busy, with Covid-19 and respiratory syncytial virus (RSV) also spreading widely over winter.

Health NZ reported just over 100 Covid cases in hospital as of last Sunday - still roughly one-quarter of the number recorded at the last wave’s peak in late May.

ESR’s latest surveillance showed while numbers of acute RSV cases among kids had crept up in Auckland over mid-August, levels were still generally low.

Jack said health authorities continued to encourage people to stay well and out of hospital by getting vaccinated and following other public health advice.

Royal New Zealand College of General Practitioners medical director Dr Luke Bradford. Photo / George Novak

“Getting immunised against influenza, which remains free for everyone aged 65 and over, pregnant people and many others, provides good protection against various strains of flu that are currently circulating,” she said.

“Annual influenza vaccination is recommended for everyone over 6 months of age.

“It’s not too late to get your influenza vaccination.”

Before Covid-19 arrived, flu was New Zealand’s single deadliest infectious disease, killing around 500 Kiwis each year.

Health experts have suggested Covid could again claim more lives than flu in 2024, although the toll could be slightly lower than the 1300-plus deaths reported last year.

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.