Flu Influenza

Overview

Flu (influenza) is a common illness caused by a virus that infects your nose, throat and lungs. It usually comes on suddenly — you can feel fine in the morning and quite unwell by the afternoon. Flu is not the same as the common cold. Cold symptoms tend to build slowly and stay mild, while flu hits faster and makes you feel much more tired and achy. Most healthy people get better on their own within about a week to ten days, but flu can make some people very unwell.

Yes. Flu is very common and spreads in waves, usually during the colder months. Most people catch flu at some point in their lives, and some people catch it more than once because the virus keeps changing.

Anyone can get flu, including healthy children and adults. Some people are more likely to become seriously unwell: children under five (especially babies under two), adults over 65, pregnant women, people with long-term conditions such as asthma, heart or kidney disease, diabetes or a weakened immune system, people living in care homes, and people who smoke. Health and care workers are also more likely to be exposed.

Symptoms

Common symptoms

• A sudden high temperature (fever) or feeling hot and shivery
• Aching muscles and joints, often feeling like you have been bruised all over
• A headache
• Feeling very tired or exhausted — this can be severe
• A dry, chesty cough
• A sore throat
• A runny or blocked nose
• Chills and sweating
• Losing your appetite
• Feeling sick or being sick, and sometimes diarrhoea

Symptoms in children

• Fever, sometimes with no other obvious symptoms at first
• Being irritable, clingy or much less active than usual
• Not wanting to feed or drink
• Earache
• Tummy pain, feeling sick or being sick
• A dry cough and sore throat
• Some young children have a febrile fit (a convulsion) when their temperature rises quickly — this needs medical help the same day

Symptoms in older adults

• Fever may be low or absent — older adults can be unwell without a high temperature
• New confusion, drowsiness or dizziness, which should always be checked
• Falls or difficulty staying steady on your feet
• Worsening of an existing condition, such as breathing problems or heart failure
• Loss of appetite and drinking less, leading to dehydration
• Cough, weakness and feeling generally 'not yourself'

Causes

Main causes

• Influenza viruses (mainly types A and B) infect the cells lining your nose, throat and airways.
• The virus spreads in tiny droplets when an infected person coughs or sneezes, and you breathe them in.
• It also spreads by touch — from hands or surfaces that have the virus on them to your mouth, nose or eyes.
• You can pass flu on from about a day before your symptoms start, and for several days afterwards — children can be infectious for longer.

Risk factors

• Being very young (under five) or over 65
• Being pregnant, at any stage
• Long-term conditions such as asthma, COPD, diabetes, heart, kidney or liver disease
• A weakened immune system, for example from some medical treatments or conditions
• Living in a care home or other shared accommodation
• Smoking
• Being very overweight
• Working in health or social care, or being in crowded indoor places during flu season

When to see a doctor

See a doctor urgently if:

• You are in a higher-risk group (for example pregnant, over 65, or have a long-term health condition) and think you have flu — contact your doctor promptly, as early advice matters.
• You have fast or difficult breathing, chest pain, or feel very unwell very quickly.
• You cannot keep fluids down or show signs of dehydration.
• You become confused, very drowsy, or hard to wake.
• A fever in a baby under three months, or any baby who is floppy, feeding poorly or breathing fast.
• Symptoms that start to improve and then suddenly get worse.

Book a routine appointment if:

• Your symptoms are not improving after about a week.
• You keep getting a fever after it seemed to settle.
• You have earache, sinus pain or a cough that lingers.
• You are unsure, or you are worried about yourself or your child.

Diagnosis

Usually flu is diagnosed from your symptoms and the time of year — during flu season, a sudden high fever with aching muscles and a cough is very likely to be flu, and no test is needed. A doctor may ask about your symptoms, check your temperature and breathing, and listen to your chest with a stethoscope.

Tests that may be done

• A swab from the back of your nose or throat, which can confirm flu — this is used mainly in hospital or when the result would change your care
• A chest X-ray if a chest infection (pneumonia) is suspected
• Blood tests, in some cases, if you are very unwell or have other conditions
• Oxygen level check (a small clip on your finger), if your breathing is affected

What to expect at your appointment

If you are usually healthy, expect a short conversation about your symptoms rather than tests. If you are in a higher-risk group or very unwell, your doctor may examine you more closely and may offer treatment or monitoring. It is helpful to mention any long-term conditions, pregnancy, or medicines you take.

Treatment

Most people get better with time, rest and simple self-care. The aim is to ease your symptoms, keep your fluids up, and watch for signs of anything more serious. If you are in a higher-risk group, your doctor may suggest a prescription antiviral medicine — these are medicines that attack the flu virus itself — which work best when started early in the illness. Antibiotics do not help flu, because flu is caused by a virus, not bacteria.

Self-care at home

• Rest as much as you need — going back to normal too soon can make you feel worse for longer.
• Drink plenty of fluids, such as water, squash or warm drinks, to replace what you lose through fever and sweating.
• Keep warm and comfortable, but do not overdress if you have a fever.
• Ask your pharmacist about over-the-counter medicines to ease fever and aches, and about which ones are safe for you — especially if you are pregnant, have other conditions, or are treating a child.
• A warm drink with honey and lemon can soothe a sore throat and tickly cough (do not give honey to babies under one year).
• Stay at home while you feel unwell, to rest and to avoid passing flu to others.
• Avoid smoking and smoky rooms, which make coughing worse.
• Take time off work or school until you feel well enough — usually around a week.

Medical treatments

Treatment depends on how unwell you are and whether you are in a higher-risk group. For most people, a doctor will advise rest, fluids and symptom relief, and will explain what to watch out for. For people at higher risk of complications, or those who are seriously unwell, doctors may prescribe antiviral medicines, which can shorten the illness and reduce the chance of complications — they work best when started within the first couple of days. If you become breathless, very unwell, or develop a chest infection, you may need to be assessed in hospital for oxygen, fluids or other support. Your doctor will explain what is right for your situation, and your pharmacist can advise on symptom relief that is safe for you.

When is surgery considered?

Surgery is not used to treat flu. Very rarely, flu leads to a serious complication that needs hospital care, and specialists will discuss any procedures with you if that happens.

Living with this condition

The first few days are usually the worst. Plan to be off your feet, keep drinks within easy reach, and ask someone to help with shopping or childcare if you can. Expect to feel tired for a week or two after the fever has gone — build your activity back up gradually rather than all at once.

Lifestyle tips

• Sleep and rest are part of the treatment, not a luxury — give yourself permission to stop.
• Keep rooms aired and avoid crowded places until you feel better.
• Wash your hands often, and cover coughs and sneezes with a tissue, to protect people around you.
• Avoid close contact with people who are vulnerable, such as newborns, older relatives, or anyone having treatment that weakens their immune system.
• Smoking and vaping irritate your airways and slow recovery — this is a good time to ask for help to stop.

Diet and exercise

There is no special diet for flu, but eating lightly and regularly helps — soup, toast, fruit and yoghurt are all fine if your appetite is low. The most important thing is drinking enough. Do not worry about exercise while you are unwell; rest instead. Once your fever has gone and you feel ready, start with short walks and gentle activity, and increase slowly over a week or two. If you feel breathless or exhausted, stop and rest.

Mental health and emotional wellbeing

Being ill with flu can leave you feeling low, anxious or isolated, especially if you are stuck at home or worried about work, money or caring for others. Feeling worn out emotionally as well as physically is common and usually passes as you recover. If these feelings are strong or not lifting, tell your doctor — support is available. If you ever feel you cannot cope or have thoughts of harming yourself, contact your local crisis line or emergency services right away, or reach out to someone you trust and ask them to stay with you.

Prevention

You cannot fully prevent flu, but you can lower your chances of catching it and of passing it on. Regular handwashing with soap and water, covering coughs and sneezes, and staying home when unwell all help. Cleaning frequently touched surfaces and letting fresh air into rooms also reduces spread.

Vaccines

A flu vaccine is offered each year, usually in autumn, because the virus changes and protection fades over time. It is recommended for people at higher risk — including older adults, pregnant women, young children, people with long-term health conditions, carers and health workers — and the age groups offered it vary by country. The vaccine cannot give you flu. Ask your doctor, pharmacist or local health service whether the flu vaccine is recommended for you this year.

Screening programmes

There is no screening test for flu. Testing is only used to help make decisions about care when someone is very unwell or in a higher-risk group.

Complications

If left untreated

• A chest infection (pneumonia), which can be serious, especially in older adults
• Bronchitis and a cough that lingers for weeks
• Ear infections and sinus infections
• Dehydration from fever, sweating and drinking less
• Worsening of long-term conditions such as asthma, COPD, diabetes or heart disease
• Rarely, inflammation of the heart, brain or other organs
• In pregnancy, a higher chance of complications for both mother and baby

Long-term outlook

For most people, flu is unpleasant but short — you should feel much better within about a week, though tiredness can linger a bit longer. Even if you develop a complication, it can usually be treated, especially when it is picked up early. Knowing the warning signs and getting advice quickly if you are in a higher-risk group gives you the best chance of a smooth recovery.

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