Flu season peak passes but . . .
The country’s flu outbreak has peaked now the midpoint of winter has passed, but New Zealand is not yet ‘‘out of the woods’’, an expert says.
In the week ending July 31, the number of influenza A detections decreased in all regions, surveillance data collated by the Institute for Environmental Science and Research (ESR) showed.
ESR virologist Dr Sue Huang said while New Zealand was over the peak of flu seen earlier this winter, the country was ‘‘not completely out of the woods yet’’.
And with six to eight weeks of flu monitoring still to go, it was not known whether another wave was coming, she said.
Influenza is not notifiable, meaning ESR data only counts tests voluntarily reported – it does not show magnitude of disease.
ESR data showed four cases of influenza A in Auckland in the week ending July 31, down from a peak of 134 five weeks ago.
Waikato saw the highest peak of flu, with 322 cases in mid-June, falling to 24 by July 31.
Wellington saw two cases, while 30 were reported in Christchurch and 26 in Dunedin.
In the week ending July 31, the rate of hospitalisations due to severe acute respiratory infections remained within the low seasonal range – about seven hospitalisations per 100,000 – but rates among under-5s ‘‘remain high’’. Respiratory Syncytial Virus (RSV) was detected in all regions over the past two weeks, with increasing cases in Waikato over the past four weeks.
There were 60 counts of RSV recorded in Waikato in the week ending July 31, up from 53 the week prior, compared with cases in the single digits in Auckland, Wellington, Christchurch and Dunedin.
There had also been 17 cases of H1N1 (swine flu) detected this winter, which Huang said was ‘‘very typical’’. In 2019, there were 128 H1N1 cases reported. It was the predominant strain in Aotearoa’s 2014 flu season, driving nearly 70% of infections.
Huang said cases of H3N2 – the dominant strain this winter – would likely gradually continue to fall, but flu cases could increase again if there was a surge of influenza B or H1N1.
To date, 24% of all Kiwis have been vaccinated against flu this season and 70% of over 65s.
While the number of flu jabs given (1.23 million) is higher than the previous two years (1.16 million in 2020 and 911,046 in 2021), some 770,000 doses remain unused.
Pharmac director of operations Lisa Williams said it anticipated some vaccine would not be used this season: ‘‘We believe that it is better to have too much vaccine than to run out.
‘‘The challenge, however, is to find the ‘sweet spot’ of not significantly over-estimating demand.’’
Although people got the most benefit from having the flu vaccine before the season started, it was still recommended people got immunised even this late, Te
Whatu Ora’s National Immunisation Programme acting director Rachel MacKay said.
She said when there was an outbreak early in the season, there was sometimes a second peak later on. While most flu this year had been influenza A, the vaccine could protect people from strains which may circulate later.
Similarly, getting the flu shot every year helped build up additional immunity over time, MacKay said: even if this was the first year someone had the vaccine, it would be useful for future years.