Dr Hannah Cooper, a public health physician in the health intelligence team at PHF Science, told RNZ there were a few different ways of defining a “bad” flu season.<\/p>\n
This season was bad because a lot of people were getting flu at once – but there was no conclusive data yet to show this particular strain was making people sicker than in previous years.<\/p>\n
What’s making this flu season so bad?<\/p>\n
Officially, flu season in New Zealand runs from May to October.<\/p>\n
The virus causes symptoms like a fever, runny nose, cough or upset stomach, and there are many different types or strains circulating each year.<\/p>\n
Each flu season is influenced by the one before. Last year, we saw the emergence of a strain of flu known as “Super-K”.<\/p>\n
It peaked late, causing an extended flu season that means people have retained some immunity from last year’s infection further into this year.<\/p>\n
But because the season has peaked later in the year, the immunity boost those of us who got the flu vaccine gained at the start of winter has worn off a bit, leaving us more vulnerable.<\/p>\n
Cold weather can’t give you the flu, but it can make it spread faster.<\/p>\n
According to Cooper, the cold snap felt around the country in early August would have increased transmission.<\/p>\n
That’s around the point when ambulance callouts began peaking, too, to reach an all-time high the week of 10 August.<\/p>\n
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Viruses spread quicker in winter due to cold temperatures and air ventilation. (Source: istock.com)<\/p>\n
Viruses spread more easily in cold weather, as low temperatures and dry air help viruses survive longer, while weakening your body’s natural defenses at the same time.<\/p>\n
People also spend more time inside when it’s cold, sharing poorly ventilated air, which increases the chance of infection.<\/p>\n
This, plus patchy vaccine uptake, aided transmission in the community.<\/p>\n
As of 6 September, 1,256,766 people had received the flu vaccine – less than a quarter of the population – most of them in May.<\/p>\n
Even though the H3 subclade, the dominant strain this year, was around last year, New Zealanders still seemed broadly susceptible to it, Cooper said.<\/p>\n
That said, the vaccine appeared to be a good match. Cooper stressed flu vaccines were better at reducing serious illness than preventing infection, so the high numbers of flu didn’t necessarily mean this vaccine wasn’t as effective.<\/p>\n
So far, the data showed the dominant strain of flu appearing in hospitals was one that was covered by the vaccine.<\/p>\n
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This year’s flu season seems more severe because health workers are already under pressure. (Source: istock.com)<\/p>\n
How does this flu season stack up compared to those in the past?<\/p>\n
That question, Cooper said, was very hard to answer.<\/p>\n
Flu cases had been tallied using different methods over the years.<\/p>\n
These days, it was done by the SARI method – that is, those presenting with Severe Acute Respiratory Infection – in the Auckland region, as a representative snapshot of the wider population.<\/p>\n
“I don’t think that anyone would be able to say how this year compares to say 20, 30 years ago.”<\/p>\n
The country’s population dynamic was also changing over time, in terms of size and co-morbidities and age structure. That meant the impact of a bad flu season in terms of pressure on hospitals in 2026 was probably quite different than it might have been in previous decades, Cooper said.<\/p>\n
How much pressure is it putting on hospitals?<\/p>\n