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When is flu season?

Approved by our Clinical team | Aug 4, 2020

Each year, seasonal flu affects hundreds of thousands of people across the globe. In most cases the virus causes mild illness that doesn’t require medical attention or hospitalisation. For certain people in high-risk groups, however, catching the flu can lead to life-threatening complications.

To avoid becoming seriously ill, it’s advised that people in high-risk groups (e.g. pregnant women, over-65s, those with long-term health conditions) receive the free flu vaccine before flu season begins.

When is flu season in the UK?

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Flu season in the UK (and across the northern hemisphere) falls between December and March. During this time, outbreaks of the flu are common. You might notice that more of your co-workers, family members and friends get sick, experiencing coughing, sneezing, headaches, fever and aches and pains.

In other parts of the world, most notably the southern hemisphere, flu season will fall at a different time of the year. The general rule is that flu outbreaks are more prevalent when the weather is cold.

When does flu season end?

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Though December-March is the peak season for flu, outbreaks can occur as late as May. Flu viruses can also begin to spread in early autumn, usually from October onwards.

It’s also worth noting that – although the flu is far more common during the autumn and winter – you can contract the virus at any time of the year if you come into contact with someone who is infected.

How long does flu season last?

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The flu season in the UK typically lasts for 4-8 months, as outbreaks can occur from December to May. But you can catch flu at any time of year.

Why is flu seasonal?

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It’s thought that the flu is more common in colder months for two reasons:

Cold, dry air helps to preserve the virus
During cold weather we spend more time indoors with other people

Cold air

The flu virus is spread via droplets of fluid, expelled from the nose or mouth in a cough or sneeze (and even by talking). It’s thought that in the winter months, the low temperatures help to preserve the virus as these droplets travel through the air. This means the virus particles can travel greater distances and survive for longer outside of the body.

Indoor spaces

Additionally, spending more time inside – whether it’s in a cinema, pub, or round the dinner table – means that we’re constantly in close contact with other people. This heightens the risk of transmission.

It’s important to note that simply being cold will not cause you to catch the flu. To become ill, you have to be exposed to the virus.

Can you catch the flu twice in one season?

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Yes, this is possible – although it is unlikely.

The reason for this is that the flu is not one virus, but rather a family of viruses which all affect the body in the same way. There are four main types of influenza virus – A,B,C and D – and each year, viruses from the A and B groups are responsible for causing flu outbreaks amongst humans. Within the A and B groups, multiple strains can end up circulating at the same time.

This means that it’s possible to catch one strain of the flu, become ill and recover, then catch a different strain later on during the same flu season. This is also the reason why a new flu vaccine is created each year, and can only offer protection for one season.

How to stay protected this flu season

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If you’re concerned about catching the flu, the best thing you can do is get the flu vaccine. You should aim to get the vaccine between October and November, however you can get it at any point during flu season.

The flu vaccine can be administered very quickly and easily – it is given as one injection in the upper arm and rarely causes side effects.

For people in high-risk groups, the flu vaccine is free on the NHS. People who don’t qualify for a free flu jab can pay for the vaccine.

Remember each year a new vaccine is created to offer protection against strains of the flu that will be prevalent in the upcoming flu season. To stay protected, you will need to get the vaccine every year.