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As we move into the spring / summer period, where the flu is always rare in New Zealand, Professor Michael Baker offers his analysis on the numbers of the flu season and why masks are still so important.
He said there has been “near extinction of influenza in New Zealand after our very effective response to Covid-19” as the numbers disappeared from the two standard surveillance systems, resulting in a reduction of 99.8 per percent in cases of influenza.
According to Baker, there were generally 1,600 more deaths in winter, compared to other seasons, and about a third of them were caused by influenza, mostly in older people with long-term health problems.
“What the response to Covid-19 has done has largely eliminated excess winter deaths and overall mortality is down about 5 percent,” he said. “That means 1,500 more people will survive this year than they hadn’t.”
Baker said these measures had led to “a revolutionary change in thinking about how to deal with respiratory pathogens” and could recover in the event of a severe flu pandemic.
“These are not measures that I would implement routinely, of course, but if we had a particularly severe respiratory illness like a severe flu pandemic … and it had the same risk of death from infection that we have seen with Covid, it is percent or one percent of people who die, then we might think about using these measures again. “
However, despite the decline in flu numbers, lockdown measures had failed to stop colds and common respiratory illnesses, such as rhinoviruses, which had decreased slightly during the lockdown but recovered shortly thereafter.
“A lot comes down to their reservoirs and some are so well adapted to humans and so widespread in the population that they are not much affected by the closure.”
He said that during the shutdown, an increase in rheumatic fever cases was seen, and this was likely due to people staying home, often in overcrowded homes, increasing their risk. This may also have been affected by less access to routine medical care for treatment and throat swab.
“Certainly some pathogens are not affected at all by the blockage,” he said.
“These viruses are more primitive, they lack this lipid membrane and that means that they are less able to evade the human immune system, but it also makes them survive better in some conditions.”
As for flu, Baker said the numbers are likely to remain very low as we move into spring and summer, but what happens next year will depend on the country’s continued response to border control.
“Rates are likely to remain very low this coming 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 these viruses out at borders and that we can also eliminate them if we get clusters of cases.”
