We’re halfway through winter but seasonal illnesses aren’t done yet

Friday, 12 July 2024

New Zealand isn't yet out of the woods for winter illnesses, experts say.

The shortest day is behind us, and this weekend marks roughly the halfway point through winter.

But that doesn’t mean the winter ills are behind us just yet.

While our winter Covid-19 wave has peaked, we’re still in a “higher prevalence” period of the virus, as we’re seeing a “rise” in winter illnesses including RSV, flu and whooping cough.

Here’s what’s going on at the moment.

What’s happening with the flu?

Though we think of winter as being June to August, New Zealand’s “flu season” is considered to be May to October, with most cases occurring during these months.

About 1 in 4 Kiwis get influenza each year.

Flu activity this year was shaping up to be “high”, said virologist Dr Sue Huang, from the Institute of Environmental Science and Research (ESR).

About one in four New Zealanders are infected with influenza each year.

Overall, the rates of hospitalisations with severe acute respiratory infections (SARI) of any cause was in the medium activity level, but nearing the “high” zone, Huang said.

This year, we have two influenza A viruses co-circulating, H1N1 (known colloquially as “swine flu”) and H3N2.

H3N2, which hits older people particularly hard, had emerged as a “much stronger runner” in the last three weeks, Huang said.

That both were in the mix could be contributing to why our flu activity is looking high this season, she said.

When will flu peak?

Institute of Environmental Science and Research (ESR) data from 2023 showed influenza cases peaked in week 26, roughly the last week of June, with 714 cases that week.

Virologist Dr Sue Huang says we’re not quite at the peak of flu season just yet.

However, there were still roughly between 500 and 600 weekly cases through the month of August 2023, ESR’s virology reporting showed.

There continued to be more than a hundred influenza cases each week until about early October.

Before the Covid-19 pandemic, the flu season typically peaked around late July or early August, Huang said.

But since the arrival of Covid-19, these peaks have moved forward.

Huang thought Aotearoa was “entering the peak period” now.

It wasn’t clear though when flu would truly peak, as activity was “still moving upwards in intensity” at the beginning of July, but Huang suggested things could perhaps in 2-3 weeks’ time.

“Let’s hope the school holidays will help to calm down the situation a bit more.”

ESR’s most recent data this year is to week 27 — with 807 flu cases reported that week.

What about RSV?

The rate of hospitalisations from severe acute respiratory infections in Auckland is in the “medium” seasonal activity range.

Huang said New Zealand’s RSV season started earlier this year than in previous years.

So far, ESR reported 5404 cases of RSV (in the week ending July 7).

In a comparable period of time last year, there had been 2741 RSV cases.

Huang thought RSV cases peaked about late June, as the level of increase in cases was now “not as big” as it was before, which was “good news”.

What’s Covid-19 doing?

Health New Zealand’s most recent reported Covid-19 data, from Monday, showed the seven-day rolling average number of new cases, hospitalisations, and total cases reported was down on the week prior.

Wastewater data in the week ending July 7 showed levels of Covid-19 had decreased again nationally for the fourth consecutive week, Dr Joanne Hewitt, Science Leader, Health and Environment, at ESR said.

This surveillance showed a peak in wastewater detections in about mid-May, and another bump in early June.

Health New Zealand hospital and specialist services spokesperson Duncan Bliss said there’s been an increase in the number of Covid and winter-related illnesses in hospitals over the past few months, as anticipated.

Bliss said they expect these winter-related demands on hospitals to remain “for some time” while seasonal illnesses continue to circulate in the community.

However, there had been a “significant decrease” in the number of inpatients with Covid-19, from a peak in early June of 386 to 165 as of July 10, “which is encouraging”.

Health New Zealand says Covid-19 cases will continue to fluctuate, so it remains “vital” people protect themselves by being up-to-date with vaccinations, and follow public health advice, such as staying home if sick.

They say that while it’s encouraging to see “any reduction” in Covid-19 cases and hospitalisations, it expects that cases are likely to increase again in future as new variants emerge and people’s immunity wanes.

‘Concerning increase’ in whooping cough

Officials have also been keeping keeping an eye on a “concerning increase” in the number of whooping cough (pertussis) cases in New Zealand.

So far this year, to July 5, there had been 227 cases of pertussis reported. That’s compared to 141 cases in all of 2023.

In April 2024, there were 22 cases of whooping cough, this jumped to 72 in May and 83 in June, ESR’s dashboard reported.