Influenza (flu): symptoms, how long it lasts, treatment and prevention

The NHS says flu symptoms come on very quickly. They can include a sudden high temperature, an aching body, feeling tired or exhausted, a dry cough, a sore throat, a headache, difficulty sleeping and loss of appetite. NHS inform adds chills, a runny or blocked nose, sneezing, feeling and being sick, diarrhoea or tummy pain.

The NHS says the symptoms are similar for children, but they can also get pain in their ear, sore eyes and swollen glands, and appear less active.

Influenza is an acute respiratory illness caused by influenza viruses, according to NICE CKS. It describes three types: influenza A, which occurs more frequently and is more virulent, influenza B, which generally causes less severe illness, and influenza C, which usually causes a mild or asymptomatic infection similar to the common cold. In the UK it usually occurs in the winter months, typically between December and March.

NHS inform says flu can affect people of any age but is more common, and can be more serious, in babies and young children, older people, pregnant women (or up to 2 weeks after giving birth), people with other health conditions such as asthma, cystic fibrosis or heart, kidney or liver conditions, and people with a weakened immune system.

The NHS says cold and flu symptoms are similar, but flu tends to be more severe.

NHS inform says the symptoms of flu usually develop 1 to 3 days after becoming infected, and most people will feel better within a week. You may have a lingering cough and still feel very tired for a few more weeks. NICE CKS says people with flu should stay off work or school until the worst symptoms have resolved (usually about 1 week).

The NHS says to ask for an urgent GP appointment or call 111 if your symptoms do not improve after 7 days.

Yes, very. The NHS says flu is very infectious and easily spreads to other people. You are more likely to give it to others in the first 5 days after getting infected. It is spread by germs from coughs and sneezes, which can live on hands and surfaces for 24 hours.

To reduce the risk of spreading flu, the NHS says wash your hands often with warm water and soap, cover your mouth and nose with a tissue when you cough or sneeze (or use the bend of your elbow), and bin used tissues quickly. Try to stay at home and avoid contact with other people if you have a high temperature, feel hot, cold or shivery, or do not feel well enough to do your normal activities.

The NHS suggests resting and sleeping, taking paracetamol or ibuprofen to lower your temperature and treat aches and pains, and drinking plenty of water to avoid dehydration (pee should be light yellow or clear). Do not give aspirin to children under 16. A pharmacist can advise on flu remedies, and you should not take paracetamol and flu remedies that contain paracetamol at the same time.

Antibiotics do not work for viral infections such as flu, and the NHS says GPs do not recommend them because they will not relieve symptoms or speed up recovery. NICE CKS says antiviral drugs (oseltamivir or zanamivir) are not usually recommended for otherwise healthy people, but may be prescribed for people in an at-risk group when flu is circulating and treatment can start within 48 hours of symptom onset.

The NHS says to ask for an urgent GP appointment or get help from NHS 111 if you or your child have symptoms of flu and you are worried about a baby or child, are 65 or over, are pregnant or have recently given birth, have a long-term medical condition such as diabetes or a heart, lung, liver, kidney, brain or nerve condition, have a weakened immune system, feel very unwell, feel short of breath, or symptoms do not improve after 7 days.

Call 999 or go to A&E if you get sudden chest pain, severe difficulty breathing (gasping, choking or not able to get words out) or start coughing up blood. NHS inform also lists feeling more drowsy than usual or finding it harder to wake up, and lips or skin turning very pale, blue or grey. Do not drive yourself to A&E.

NHS inform says people at higher risk are more likely to have complications such as pneumonia or worsening of lung problems, usually after a few days of symptoms. NICE CKS lists most adult complications as respiratory: acute bronchitis, pneumonia, exacerbations of asthma and COPD, otitis media and sinusitis, and says urgent admission should be considered if pneumonia or another complication occurs.

The NHS says the flu vaccine helps protect against flu, which can be serious or life-threatening, and is offered on the NHS every year in autumn or winter to people at higher risk. You can get the free adult vaccine if you are aged 65 or over, aged 18 to 64 with certain long-term health conditions, pregnant (at any stage), living in a care home, the main carer for an older or disabled person, living with someone who has a weakened immune system, or aged 16 or over and rough sleeping or in a hostel.

You can book online or in the NHS App, find a pharmacy offering it, or contact your GP surgery. NHS inform says the annual vaccine can help reduce your risk of getting flu each year.

Most people can manage flu at home with advice from a pharmacist. The NHS provides the vaccine free to eligible groups through GP surgeries and pharmacies.