Will a new mutated flu strain cause a harsh winter?

The flu strikes every winter, but something seems to be different this year.

A seasonal flu virus suddenly mutated in the summer; it seems to evade part of our immunity; A flu season has started more than a month in advance and it is a type of flu that, according to history, is more serious.

The NHS has now issued a ‘flu SOS’ as fears grow that this will result in a brutal winter.

There is a lot of nuance and uncertainty, but leading flu experts have told me they wouldn’t be surprised if this was the worst flu season in a decade.

“We haven’t seen a virus like this for a long time, this dynamic is unusual,” says Professor Nicola Lewis, director of the Francis Crick Institute’s Global Influenza Centre.

“It absolutely worries me,” he says. “I’m not panicking, but I’m worried.”

So what’s going on? And what can we do?

Scientists track the evolution of flu viruses because they constantly mutate and the seasonal flu vaccine must be updated each year to keep up.

This evolution occurs in a rhythm known as “shift and drift.”

Most of the time, the virus progresses by making minor changes and then every now and then there is a sudden and abrupt change as the virus mutates substantially.

That happened in June of this year.

Seven mutations appeared in a seasonal H3N2 flu strain and caused a “rapid increase” in reports of the mutated virus, says Professor Derek Smith, director of the center for pathogen evolution at the University of Cambridge.

Unusually, this occurred outside of flu season, in the middle of the northern hemisphere summer.

“It will almost certainly spread around the world, so from that point of view it is something that will happen quickly,” Professor Smith says.

In September, as children returned to school, the nights drew in and temperatures began to drop, there was a spike in cases.

Exactly what the mutations do is still being explored, but they are likely helping the virus evade some of the immunity we have developed over years of infections and flu vaccines.

The result is that the virus finds it easier to infect people and spread; This is why the flu season is so early in the UK and other countries, including Japan.

If the virus can spread more easily, then you don’t have to wait for more favorable winter conditions (when we spend more time indoors with the heat on and windows closed) to start flu season.

“We’re way ahead,” says Professor Lewis, “I think it’s going to be a strong flu season.”

If you remember the pandemic’s R numbers (that is, the number of people each infected person passes the virus to), they suggest the new mutant has an advantage.

Seasonal flu usually has an R number of around 1.2, while the initial estimate for this year is 1.4, Professor Lewis said.

Generally speaking, if 100 people had the flu, they would pass it on to 120 in a normal year and 140 this year.

“It is very likely to be a bad flu season and it will happen very soon, we are already in it,” says Professor Christophe Fraser, from the Institute of Pandemic Sciences at the University of Oxford.

“There are indicators that this could be worse than some of the flu seasons we’ve seen in the last 10 years.”

In a typical flu season, about one in five people is infected, but that number could be higher this year, he warns.

But all of these predictions are still clouded by uncertainty.

Some are looking to Australia for clues, as this year had the worst flu season on record, although it did not face the same H3N2 mutation that we have.

We know that the virus is spreading very well among children in the germ fest that is the schoolyard.

But the immunity a 10-year-old has developed will be very different from that of his grandparents, whose immune defenses may have been shaped by six times as many flu seasons.

Therefore, experts will monitor closely as the virus begins to infect older age groups in the coming weeks.

History suggests that the form of influenza we face this year is more serious, particularly for older people.

There are several types of flu and you may have heard some of the names, such as H1N1 swine flu, which caused a pandemic in 2009, or H5N1, which is the current flu killing birds around the world.

The new mutations have occurred in a group of H3N2 flus.

“H3 is always a hotter virus, it’s a nastier virus and it has more of an impact on the population,” Professor Lewis said.

It’s worth remembering that some of us will catch the flu and not develop any symptoms, while others will have a sudden fever, body aches and exhaustion, but the virus can be deadly in older and more vulnerable groups.

Last year, almost 8,000 people died from the flu, and in the 2022-23 flu season there were almost 16,000 deaths. The NHS is already predicting a tough flu season.

So what can we do about it?

The clear advice is to get vaccinated against seasonal flu – NHS England issued a “flu SOS” saying there were 2.4 million vaccine slots available next week.

Professor Lewis maintains that this is “absolutely the most important year” to get vaccinated and that “if your GP has called you, get your flu vaccine as soon as possible.”

However, this year’s vaccine does not perfectly match the mutated virus.

The decision on the vaccine design was made in February to allow enough time to produce the millions of doses needed, and then the new mutant emerged in June.

“Some protection is better than no protection, but this year is likely to be one of the years where the amount of protection is less than in years where the match is better – it’s not an ideal situation,” Professor Fraser said.

The vaccine will continue to cause the body to produce antibodies that can recognize the flu and stick to it.

But the biggest benefits are expected to be in lessening the severity of the disease rather than preventing you from getting sick or slowing the spread of the virus.

Meanwhile, doctors have been advised that early antiviral treatment reduces the risk of flu complications.

Japan is also experiencing an early flu season and has closed schools to help contain outbreaks.

These are not Covid-style lockdowns, but rather short-term measures the country is using to slow the spread of the virus.

No one knows for sure what will happen in the coming months.

“This may all go away next week,” says Professor Lewis, “but I don’t think it will.”