What is super flu? And other questions answered

The NHS is facing severe pressure this winter as flu cases surge earlier than usual, with some calling it “super flu”. Here’s what you need to know about this year’s flu season and how to protect yourself.

What is ‘super flu’?

Professor Meghana Pandit, NHS national medical director, said: “With record demand for A&E and ambulances and an impending resident doctors strike, this unprecedented wave of super flu is leaving the NHS facing a worst-case scenario for this time of year.”

Although this term has now been repeated frequently in the media, it was not intended as a new scientific designation. Although the flu season began early, both the spread of the virus and the severity of illness remain within what experts consider normal for a flu season.

Influenza viruses are constantly evolving to evade our immune system, which is why the flu vaccine must be updated regularly. Some years the virus mutates more than others, and it typically undergoes a major change every four to five years.

The “subtype” of flu that is dominant this year, called influenza A/H3N2, has been around since 1968 and there have been over a dozen such changes in that time. By this definition, we see “super flu” every few years.

Is the situation in the UK really as bad as some headlines suggest?

The situation isn’t unprecedented – it falls within the range of what scientists would expect in a bad flu season.

Because the season started early, it is misleading to directly compare the number of cases and hospitalisations to the same week in previous years. In fact, the situation is comparable to previous years after taking the early season start into account, as a recent analysis my colleagues and I conducted shows.

Which areas of the UK are worst affected?

The most important consideration from a public health perspective is the burden on healthcare systems in different regions, which is determined by what the virus is doing and what resources are available in those regions.

The available data only provides general infection trends at regional levels. England’s influenza season started earlier than in Scotland, Wales and Northern Ireland, so we might expect the situation to turn earlier in England than elsewhere.

Based on the data for England from the UK Health Security Agency, the north and the Midlands are possibly experiencing higher flu rates – but not significantly so.

Why are we seeing more flu cases in younger people?

Children and teens are more likely to get infected due to their high contact rates in schools, where a lot of spread happens, and also because their immune systems are less experienced at dealing with flu viruses.

Adults are less likely to become infected overall, as they typically have lower contact rates and their immune systems have more experience with influenza. However, people over 64 are more likely to have existing health conditions that put them at higher risk of severe illness if they do become infected, and their immune systems have started to weaken in a process called immunosenescence.

Babies are also at greater risk of severe illness as their immune systems are still undeveloped.

People of a similar age tend to have been infected with similar flu viruses, which might explain why certain age groups are more affected by flu than others in some seasons. It might be that the virus this year happens to have found an immunity gap in children that isn’t present in other age groups.

Vaccine effectiveness is lower for older people, so should they still get the jab?

The latest data shows that the flu vaccine reduces the risk of being hospitalised with flu by about 30 to 40% in older people. That’s lower than vaccines against some other viruses, but similar to previous years for flu.

The recommendations this year are therefore unchanged: vaccination is still the best thing you can do to protect yourself and help reduce the burden on the NHS.

Why does the vaccine have different effectiveness in different age groups?

This season’s vaccines are offering effective protection against severe flu. Children are around 70 to 75% less likely to attend or be admitted to hospital with flu if vaccinated, and, as mentioned above, adults are around 30 to 40% less likely to attend or be admitted.

Children are offered a nasal spray, whereas adults are given an injection. Studies have shown that the nasal spray vaccine works better in children and less well in adults, which is why the recommendations are different. So one reason for the difference is that we are comparing estimates from different vaccines as well as different age groups.

Another reason is differences in existing immunity. Adults have already been exposed to many flu viruses over their lives, so the incremental gain of one extra vaccine is probably smaller – but still beneficial – than for a child.

What should I do if I think I’ve caught it: call 111, stay home, or go to A&E?

Stay home if you are sick, rest, and take sensible precautions to avoid spreading the virus to others. Getting influenza is very unpleasant, but everyone will get it roughly once every five years. In the vast majority of cases, people get better on their own, without any medical treatment.

Are there test kits (lateral flow) I can buy at the pharmacy, as there were for COVID?

Yes, very similar tests exist for the flu and you can buy these at pharmacies and online. Although it’s interesting to know if it’s influenza or some other virus that is making you sick, if you have flu symptoms the advice is the same regardless of which virus caused it.

Is it too late to get the vaccine – given that it takes two weeks for the vaccine to properly kick in?

No, it’s not too late, and the sooner the better! Even after the epidemic has peaked, it will take a few months before cases reach low levels again. There is still a risk of infection in that time, so any extra protection from the vaccine is still helpful.

James Hay receives funding from the Wellcome Trust (grant 225001/Z/22/Z).