Mask wearing and social distancing for Covid-19 has all but cut influenza cases in New Zealand this year, with only six flu isolates detected in this country from April to August.
As we move into the spring/summer period where flu is always uncommon in New Zealand, Professor Michael Baker offers his analysis on the flu season numbers and why masks continue to be so important.
He said there has been "near extinction of influenza in New Zealand following our very effective Covid-19 response", as numbers vanished from the two standard systems for surveillance - resulting in a 99.8 per cent reduction in flu cases.
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According to Baker, there were usually 1600 more deaths in winter, compared to other seasons, and around a third of those were caused by influenza, mostly in older people with long-term health conditions.
"What the Covid-19 response has done has largely eliminated those excess winter deaths and mortality as a whole is down around 5 per cent," he said. "So that means an extra 1500 people will survive this year who wouldn't have."
Baker said these measures had led to "a revolutionary change in thinking about how to deal with respiratory pathogens" and could be brought back in the event of a serious flu pandemic.
"These are not measures you would roll out routinely of course, but if we had a particularly severe respiratory disease like a severe flu pandemic ... and it had the same infection fatality risk as we've seen with Covid, that is half a per cent or 1 per cent of people dying, then we could think about using these measures again."
However, despite flu numbers being down, lockdown measures had not managed to stop ordinary colds and respiratory illnesses, such as rhinoviruses - which had dropped slightly during lockdown but bounced back soon after.
"A lot does come down to their reservoirs and some are so well-adapted for humans and they're so widespread in the population that they are not affected a great deal by the lockdown."
He said that during the lockdown, a rise in rheumatic fever cases was observed - and this was likely due to people staying home, often in overcrowded homes which increased their risk. This may have also been affected by less access to routine healthcare for throat swabbing and treatment.
"Certainly, some pathogens are not affected at all by lockdown," he said.
"These viruses are more primitive, they lack this lipid membrane covering and it means that they're less able to evade the human immune system, but it also makes them survive better in some conditons."
As for influenza, Baker said numbers were likely to stay very low as we moved into spring and summer, but what happens next year would depend on the country's ongoing response to border control.
"It's likely that rates will stay very low for next winter as well, if our response continues in the same way.
"We have learned remarkable things from the Covid response, both that we can keep out these viruses at the borders and that we can also stamp them out if we get clusters of cases."