Doctors say a new variant of flu sparking infections across the UK has unique symptoms people should watch out for. The number of people in hospital with flu increased at the start of this year, with 2,924 a day hospitalised by the virus up to January 4.

Four hospital trusts have declared critical incidents due to "significant and sustained pressures" in their services. Three trusts in Surrey and one in Kent have declared critical incidents.

Surrey Heartlands Trust said high winter pressure had been 'exacerbated by increases in flu and norovirus cases'. NHS national medical director Professor Meghana Pandit said: “It’s clear that the worst is far from over for the NHS this winter, with hospitals again experiencing a rise in patients admitted with flu and other respiratory virus cases last week."

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He added: “It remains important that people come forward for care as usual and there are still plenty of opportunities to get vaccinated and get protected against flu.”

Health Secretary Wes Streeting said: “Flu can be serious, particularly for older people, young children and those with underlying conditions, and vaccination remains the best protection. I urge everyone who is eligible to get their flu jab as soon as possible.

Doctors say they have seen different symptoms with the new strain of flu. The new virus strain, subclade K, is a variant of the A H3N2 subtype of flu.

Dr Mark Loafman told NBC Chicago those with flu are experiencing 'more fever with the flu this year than people are accustomed to. And the fever can last up to seven days, so five to seven days. And that's worrisome.'

Doctors say in some cases the fever isn't brought down by usual treatments like paracetamol or ibuprofen. Lung expert Dr Juanita Mora said: "This new strain has symptoms of really high fevers. It has a really bad cough that won't go away, very phlegmy, and also vomiting and diarrhoea and lots of joint aches as well as muscle aches."

Doctors have reported more cases of patients with stomach problems - sickness and vomiting, also known as gastrointestinal or GI problems. Dr Loafman said: "We are seeing anecdotally more signs of some GI illness for the adults who have the subclade K strain of flu."

According to the NHS, flu (influenza) symptoms often come on very quickly and are generally more severe than a common cold. While most people feel better within a week, it can be a very unpleasant experience.

The main symptoms usually hit you suddenly and include:

• A sudden high temperature (38C or above)




• An aching body (muscles and joints)




• Feeling tired or exhausted




• A dry cough




• A sore throat




• A headache




• Difficulty sleeping




• Loss of appetite




• Nausea, vomiting, or diarrhoea (more common in children)

Most people can manage flu symptoms themselves without seeing a doctor. The NHS recommends the following self-care steps:

• Rest and Sleep: Give your body the energy it needs to fight the infection.




• Stay Warm: Use blankets or extra layers to keep your core temperature stable.




• Hydrate: Drink plenty of water to avoid dehydration (your urine should be light yellow or clear).




• Pain Relief: Take paracetamol or ibuprofen to lower your temperature and ease aches. Avoid taking "all-in-one" flu remedies alongside paracetamol tablets, as you could accidentally exceed the safe dose.




• Soothe a Sore Throat: Gargle with salt water (adults only) or drink hot lemon and honey.

The NHS advises calling 111 or booking an urgent GP appointment if:

• You are worried about your baby's or child's symptoms.




• You are age 65 or over.




• You are pregnant.




• You have a long-term medical condition (e.g., diabetes, heart/lung disease) or a weakened immune system.




• Your symptoms do not improve after 7 days .

Call 999 or go to A&E immediately if you develop sudden chest pain, have severe difficulty breathing, or start coughing up blood.