The mask has slipped on flu prevention

Surveillance data suggest New Zealand may finally be past the peak of a flu season that arrived later than usual and had a rapid rise in numbers, a surge that meant that within a few weeks, general practices reported overflowing waiting rooms, hospitals struggled under winter demand and influenza-related deaths climbed to levels not seen for years.

Next winter another flu season will arrive, and we will once again be asking whether our health system can cope. Why was this year’s peak so severe, and what can we learn from it?

You might have heard blame on a ‘particularly virulent’ virus, but influenza is always too complicated to put down to a particular strain of influenza virus.

This season’s dominant strain was an influenza A(H3N2) virus from the K subclade, a strain that appears somewhat more transmissible than those circulating in recent years. However, laboratory surveillance suggests the virus was genetically similar to the strain included in the 2026 Southern Hemisphere influenza vaccine, meaning the vaccine was a good match for the virus circulating in New Zealand.

What was unusual was not simply the virus itself, but the way the season unfolded.

After minimal flu activity through much of the winter, influenza arrived late and spread rapidly. That sudden acceleration placed enormous pressure on a health system already operating close to capacity. General practices, after-hours clinics and hospitals prepare for winter pressures every year. But preparation can only go so far when staffing shortages, workforce pressures and resource constraints already leave little room for unexpected demand.

But the story is not only about hospitals and viruses. It is also about us.

One of the unexpected legacies of Covid-19 was that millions of people gained more than a basic understanding of how respiratory viruses spread. We learned how one person’s cough could become another person’s hospital admission. We became familiar with staying home when sick, washing hands, improving ventilation, and wearing masks in crowded spaces.

Those habits helped reduce transmission, not only of Covid but of many respiratory infections co-circulating. Yet many of those lessons appear to have faded. Today, it is common to see people going to work, school, university lectures and social events despite having obvious respiratory symptoms. Few people are wearing masks any more. The collective effort that characterised the pandemic period has disappeared.

Public health behaviours are easier to maintain when everyone else is practising them. As fewer people are wearing masks or staying home when unwell, the norm shifts; it becomes harder for individuals to continue these precautions even when they want to.

Vaccination remains one of the most effective tools we have, particularly for older adults, babies, pregnant people and those with chronic health conditions. For elderly people, annual influenza vaccination has a positive cumulative effect of greater protection against influenza complications and hospitalisation compared with only ever being vaccinated against influenza once.

Vaccination does not always prevent you from getting the flu, but it substantially reduces the risk of severe disease, hospitalisation and death from flu and from other conditions triggered by it.

Yet vaccination rates remain disappointingly low, around 50-60 percent, depending on ethnicity, and were lower this year than last year.

Many of us still underestimate influenza.

It’s not simply a bad cold. For some people it can trigger serious complications extending beyond the initial infection. The risk of heart attack and stroke increases markedly in the week following influenza infection. By contrast, the risk of having a heart attack or a stroke is reduced by around a third with vaccination. The benefits of vaccination extend beyond avoiding a week feeling miserable in bed.

But individual responsibility alone cannot explain what happened this winter.

Many New Zealanders cannot easily stay home when they are sick. Parents often face impossible choices when a child has a mild respiratory illness but are obliged to (or need to) go to work. Crowded housing increases transmission. Economic pressure can make taking time off work difficult. Poor housing, financial stress and limited flexibility create ideal conditions for respiratory viruses to spread.

Influenza is more than a virology problem. It’s also a housing problem, a workforce problem, a public-health problem and an inequality problem. Respiratory epidemics expose the conditions in which people live and work. When large numbers of people become sick simultaneously, the consequences ripple through schools, workplaces, hospitals, and households.

The encouraging news is that seasons like this are not entirely unpredictable.

We now have an increasing ability to use a range of surveillance systems and modelling tools to identify emerging trends and provide warning of likely influenza peaks. In New Zealand, a major research programme is investigating whether hospital and primary-care surveillance data can provide one or two weeks’ notice before influenza activity surges. That may sound modest, but for stretched health services and struggling communities even a short warning period could help hospitals, clinics and communities prepare for the most demanding weeks of winter.

The broader lesson from this year’s flu season is that respiratory epidemics are rarely just about viruses.

They are shaped by vaccination rates, housing conditions, income security, health-system capacity and whether people can act responsibly when unwell. They are shaped by whether we pay attention to warnings and whether we invest in the systems that reduce harm before a crisis arrives.

If next winter proves as difficult as this one, we should not be able to say we were caught by surprise.

The challenge will be whether we act on what this season has taught us.