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In the past few weeks, I have had more than the usual number of friends cancel plans because they have come down with a bug – complaining of a streaming nose, cough, or temperature.

I wasn’t imagining it: the flu season has started earlier this year. Rates of flu infections in the UK are still relatively low but they are rising, the UK Health Security Agency said – even though it is only October.

That means that GPs – on top of the usual surge in coughs and colds that happens when children go back to school in September in most of the UK – have seen a broader rise in consultations for respiratory viruses. So, what’s the significance of the change in flu timing, and how can you tell flu from other bugs?

It may sound surprising but scientists are still debating exactly why respiratory viruses peak every winter.

There are several possible reasons. Viruses survive for longer in colder air, for instance. Winter air is also drier, which may cause virus-laden moisture droplets to evaporate and shrink into tiny particles that can float further afield.

Human nasal cells may also function less well in the cold. And a fourth theory is that our tendency to mix socially indoors rather than outdoors is enough to tip the infection rate that bit higher.

Whichever one or ones of these explanations are right, in countries like the UK, flu and other respiratory viruses tend to surge every winter, but the timing and extent of the surge is variable.

The flu cycle

While the peak is usually in December or January, it can be any time from October to March. And the number of deaths directly caused by flu also varies each year, from just a few thousand to over 15,000 in bad years.

This variation depends partly on what’s been going on in other parts of the world. Temperate countries in the Southern Hemisphere experience the same cycle in reverse, with a flu peak in their winter – June, July and August.

This is important because the circulating flu viruses accumulate small mutations all the time, called antigenic drift. The mix that predominates in the southern hemisphere’s winter predicts to some extent the mix that arrives in the UK a few months later.

One reason for flu starting early this year could be that there has been more than usual drift of H1N1, one of the three main circulating flu strains, said Dr Jamie Lopez Bernal, a UKHSA epidemiologist.

Another explanation could be that Australia and other southern hemisphere countries had a relatively late flu season in 2026, resulting in more people carrying the flu into the UK at a time when Brits become more vulnerable. “That means there’s more importation towards the start of our season,” said Lopez Bernal.

But that doesn’t mean the UK is necessarily headed for a worse flu season overall. Despite some predictions of a “superflu” year in 2026 – flu season also started early last year, and yet it ended up with a lower number of flu deaths than average.

“Activity started earlier than in the [previous] season but also declined earlier and the overall level of activity over the course of the season was lower,” said a Government report published this May.

Nonetheless, the early start is something health officials are keeping an eye on, said Dr Simon Clarke, a microbiologist at the University of Reading. “It doesn’t necessarily herald a worse flu season. But if that drifted strain isn’t protected by previous exposure or by vaccines, then it could lead to a worse season.”

How to tell flu from a cold

Flu is often mixed up with the 200-plus other viruses that cause colds and coughs – including Covid.

The main way to tell the difference is that flu is generally more severe and comes on more quickly, says Dr Dan Baumgardt, a GP and lecturer at the University of Bristol. “Flu comes on usually over a space of hours,” he says.

With flu, the most obvious symptom is a raised temperature, causing shivering, fever and muscle aches.

With coughs and colds, the main symptoms are runny nose, sneezing, coughing, and a sore throat – although they can also cause a raised temperature.

“I have colleagues who come to work claiming to have the flu,” says Clarke. “They’ve got a cold because they wouldn’t be able to get out of bed if they’ve got flu.”

Because of the flu season’s early start, the UKHSA is urging anyone eligible to take up the NHS offer of a flu vaccine as soon as possible this year.

People should not be put off if they had it in previous years and still got common colds, said Clarke. “There are so many other things out there and it won’t protect you against colds,” he says. “But flu is probably the one thing that is most likely to make you particularly unwell in winter.”

Myths to ignore about colds and flu

• Getting cold or wet can give you a cold. You need to be exposed to a virus to develop a respiratory illness. But getting seriously chilled could lower your immune defences, making you more vulnerable to catching the infection.
• The flu jab can give you flu. That’s impossible. The injectable flu vaccines use dead viruses or bits of their proteins, so they can’t start multiplying in your body. The nasal vaccine for children is live, but the virus has been changed so it can only multiply inside the nose and throat – not the rest of the body. This vaccine can, however, sometimes cause a runny nose or slight temperature – that’s a sign your immune system is reacting to it.
• A bad cold needs antibiotics. Nope. Colds, coughs and flu are all caused by viruses, which antibiotics are useless against. They only work against bacteria, which are a different type of organism from viruses. But sometimes a viral infection can lead to a secondary bacterial chest infection – then your doctor may prescribe antibiotics.

Elizabeth Strout’s best-known book is , which won a Pulitzer and was made into an HBO TV series. But I have been enjoying another book by the same author, The Things We Never Say.

This is about an older, well-to-do couple adjusting to their careers winding down and their adult son making his own separate life. It may not sound like the most exciting premise, but this small family goes through some extreme dramas, and I couldn’t put the book down.