Flu (Influenza)

Flu is a common infectious viral illness spread by coughs and sneezes. It can be very unpleasant, but you will usually begin to feel better within about a week. You can catch flu (short for influenza) all year round, but it is especially common in winter, which is why it is also known as "seasonal flu".

It is not the same as the common cold. Flu is caused by a different group of viruses and the symptoms tend to start more suddenly, be more severe and last longer. Some of the main symptoms of flu include:

• a high temperature (fever) of 38C (100.4F) or above
• tiredness and weakness
• a headache
• general aches and pains
• a dry, chesty cough.

Cold-like symptoms – such as a blocked or runny nose, sneezing, and a sore throat – can also be caused by flu, but they tend to be less severe than the other symptoms you have. Flu can make you feel so exhausted and unwell that you have to stay in bed and rest until you feel better.

What to do

If you are otherwise fit and healthy, there is usually no need to see a doctor if you have flu-like symptoms. The best remedy is to rest at home, keep warm and drink plenty of water to avoid dehydration. You can take paracetamol or ibuprofen to lower a high temperature and relieve aches if necessary. Stay off work or school until you're feeling better. For most people, this will take about a week.

When to see your doctor

Consider visiting your family doctor if:

• you are 65 years of age or over
• you are pregnant
• you have a long-term medical condition – such as diabetes, heart disease, lung disease, kidney disease or a neurological disease
• you have a weakened immune system – (e.g. you are having chemotherapy or have HIV)
• you develop chest pain, shortness of breath or difficulty breathing, or start coughing up blood
• your symptoms are getting worse over time or have not improved after a week.

In these situations, you may need medication to treat or prevent complications of flu. Your doctor may recommend taking antiviral medicine to reduce your symptoms and help you recover more quickly.

How long does flu last and is it serious?

If you have flu, you generally start to feel ill within a few days of being infected. You should begin to feel much better within a week or so, although you may feel tired for much longer. You will usually be most infectious from the day your symptoms start and for a further three to seven days. 

Children and people with weaker immune systems may remain infectious for longer. Most people will make a full recovery and won't experience any further problems, but elderly people and people with certain long-term medical conditions are more likely to have a bad case of flu or develop a serious complication, such as a chest infection.

How you catch flu

The flu virus is contained in the millions of tiny droplets that come out of the nose and mouth when someone who is infected coughs or sneezes. These droplets typically spread about one metre. They hang suspended in the air for a while before landing on surfaces, where the virus can survive for up to 24 hours.

Anyone who breathes in the droplets can catch flu. You can also catch the virus by touching the surfaces that the droplets have landed on if you pick up the virus on your hands and then touch your nose or mouth. Everyday items at home and in public places can easily become contaminated with the flu virus, including food, door handles, remote controls, handrails, telephone handsets and computer keyboards. Therefore, it's important to wash your hands frequently.You can catch flu many times, because flu viruses change regularly and your body won't have natural resistance to the new versions.

Preventing the spread of flu

You can help stop yourself catching flu or spreading it to others with good hygiene measures.

Always wash your hands regularly with soap and warm water, as well as:

• regularly cleaning surfaces such as your computer keyboard, telephone and door handles to get rid of germs
• using tissues to cover your mouth and nose when you cough or sneeze
• putting used tissues in a bin as soon as possible.

You can also help stop the spread of flu by avoiding unnecessary contact with other people while you're infectious. You should stay off work or school until you're feeling better. In some people at risk of more serious flu, an annual flu vaccine (see below) or antiviral medication may be recommended to help reduce the risk of becoming infected.

The flu vaccine

A flu vaccine is available for free on the NHS for:

• anyone over the age of 65 
• pregnant women
• anyone who is very overweight (with a body mass index over 40)
• children and adults with an underlying health condition (particularly long-term heart or lung disease)
• children and adults with weakened immune systems.

An annual flu vaccine nasal spray is also now offered to healthy children aged two, three and four years old, and to children in school years one and two. The best time to have the vaccine is in the autumn, between September and early November. If you think you might need it, contact your local GP surgery. You should have the flu vaccination every year so you stay protected, as the viruses that cause flu change every year.

Other types of flu

As well as seasonal flu, there are several other types of flu. These include:

• bird (avian) flu – a type of flu spread among birds that affects humans in rare cases
• swine flu – the type of flu that was responsible for the flu pandemic in 2009-10
• "gastric flu" (gastroenteritis) – an infection of the digestive system, which can be caused by bacteria or viruses such as the norovirus.

  

Symptoms of flu 

The symptoms of flu usually develop within one to three days of becoming infected. Most people will feel better within a week. However, you may have a lingering cough and still feel very tired for a further couple of weeks.

Main symptoms

Flu can give you any of the following symptoms:

• a sudden fever – a temperature of 38C (100.4F) or above
• a dry, chesty cough
• a headache
• tiredness and weakness
• chills
• aching muscles
• limb or joint pain
• diarrhoea or abdominal (tummy) pain
• nausea and vomiting
• a sore throat
• a runny or blocked nose
• sneezing
• loss of appetite
• difficulty sleeping.

Is it flu or a cold?

It can sometimes be difficult to tell if you have flu or just a cold, as the symptoms can be quite similar. The main differences are:

Flu symptoms:

• come on quickly
• usually include fever and aching muscles
• make you feel too unwell to continue your usual activities.

Cold symptoms:

• come on gradually
• mainly affect your nose and throat
• are fairly mild, so you can still get around and are usually well enough to go to work.

When to visit your doctor

If you are otherwise fit and healthy, there's usually no need to visit your doctor if you have flu-like symptoms. You should just rest at home until you feel better, while keeping warm, drinking plenty of water and taking painkillers if necessary. Consider visiting your doctor if:

• you are 65 years of age or over
• you are pregnant
• you have a long-term medical condition – such as diabetes, heart disease, lung disease, kidney disease or a neurological disease
• you have a weakened immune system – for example, because you're having chemotherapy or have HIV
• you develop chest pain, shortness of breath or difficulty breathing, or start coughing up blood
• your symptoms are getting worse over time or haven't improved after a week.

Treating flu 

Usually, you can manage flu symptoms yourself at home and there's no need to see a GP. Most people feel better within a week.

You should consider seeing your GP if you're at a higher risk of becoming more seriously ill. This includes people who:

• are 65 or over
• are pregnant
• have a lung, heart, kidney, liver or neurological disease
• have a weakened immune system 
• have diabetes.

In these cases, your doctor may suggest taking antiviral medication.

Managing your symptoms at home

If you are otherwise healthy, you can look after yourself at home by resting, keeping warm and drinking plenty of water to avoid dehydration. If you feel unwell and have a fever, you can take paracetamol or anti-inflammatory medicines such as ibuprofen to lower your temperature and relieve aches. Children under 16 shouldn't be given aspirin.

Stay off work or school until you're feeling better. For most people, this will take about a week. See your doctor if your symptoms get worse or last longer than a week.

Antiviral medication

In 2009, the National Institute for Health and Care Excellence (NICE)recommended that doctors shoulder consider treating people in the at-risk groups mentioned above with the antiviral medications oseltamivir (Tamiflu) or zanamivir (Relenza) to reduce the risk of complications of flu.

Antivirals work by stopping the flu virus from multiplying in the body. They won't cure flu, but they may help slightly reduce the length of the illness and relieve some of the symptoms. Recent research has suggested that Tamiflu and Relenza may not be effective at reducing the risk of flu complications and could cause side effects, so not all doctors agree they should be used.

But there is evidence that antivirals can reduce the risk of death in patients hospitalised with flu. In the light of this evidence, Public Health England says it is important that doctors treating severely unwell patients continue to prescribe these drugs where appropriate. 

Antibiotics

Antibiotics are not prescribed for flu as they have no effect on viruses, although they may be prescribed if you develop a complication of flu, such as a bacterial chest infection.

Complications of flu 

Complications of flu mostly affect people in high-risk groups, such as the elderly, pregnant women and those who have a long-term medical condition or weakened immune system.

This is why it's important for people in these groups to have the annual flu vaccination and consider seeing their doctor if they develop symptoms of flu.

Chest infections

The most common complication of flu is a bacterial chest infection, such as bronchitis. Occasionally, this can become serious and develop into pneumonia. A course of antibiotics usually cures a chest infection or pneumonia, but it can very occasionally become life-threatening, particularly in the frail and elderly.

Worsening of existing conditions

In some people with long-term health conditions, getting flu can make their condition worse.

For example, people with lung conditions such as asthma or chronic obstructive pulmonary disease (COPD) may find that their symptoms become more severe when they get the flu.

In people with diabetes, flu can affect blood sugar levels, potentially causing hyperglycaemia (high blood sugar) or, in people with type 1 diabetes, diabetic ketoacidosis (a dangerous condition caused by a lack of insulin in the body). If you have type 1 diabetes or have type 2 diabetes and take insulin, it's a good idea to monitor your blood sugar level more closely while you’re feeling unwell. 

Pregnancy complications

If you get flu while you are pregnant, there's a small risk that the infection could cause problems with your pregnancy. Flu may cause you to go into premature labour (before 37 weeks of pregnancy), or it may result in your baby having a low birth weight. Occasionally, getting flu during pregnancy can result in a miscarriage or stillbirth. 

Rare complications

Less common complications of flu include:

• tonsillitis – inflammation of the tonsils
• otitis media – an infection of the middle ear
• sinusitis – inflammation of the lining of the sinuses (small, air-filled cavities behind your cheekbones and forehead)
• febrile seizures (convulsions) – a fit that can happen when a child has a fever
• meningitis – infection in the brain and spinal cord
• encephalitis – inflammation of the brain.

Preventing flu 

There are three main ways of preventing flu: good hygiene, such as handwashing and cleaning, the flu vaccination and antiviral medication.

Good hygiene

To reduce your risk of getting flu or spreading it to other people, you should always:

• make sure you wash your hands regularly with soap and warm water
• clean surfaces such as your keyboard, telephone and door handles regularly to get rid of germs
• use tissues to cover your mouth and nose when you cough or sneeze
• put used tissues in a bin as soon as possible.

The flu vaccine

The annual flu vaccine can help reduce your risk of getting flu each year, although it's not 100% effective because it doesn't work against every possible type of flu virus. A flu vaccine is available for free on the NHS for:

• anyone over the age of 65 
• pregnant women
• anyone who is very overweight (with a body mass index over 40)
• children and adults with an underlying health condition (particularly long-term heart or lung disease)
• children and adults with weakened immune systems.

Adults over 18 and children aged six months to two years in these groups are given an annual injection, while children aged two to 18 are given an annual nasal spray. The annual nasal spray is also now given to healthy children aged two, three and four years old, and to children in school years one and two.

The best time to have the vaccine is in the autumn, between September and early November. If you think you need it, contact your local doctor's surgery. You should have the flu vaccination every year so you stay protected. The viruses that cause flu change every year, so this winter's flu will be different from last winter's.

Antiviral medication

Taking the antiviral medicines oseltamivir (Tamiflu) or zanamivir (Relenza) to prevent flu is recommended if all of the following apply:

• there is a lot of flu around
• you're over 65, pregnant, or have a medical condition that puts you at risk of complications of flu, such as diabetes, heart disease, lung disease, kidney disease or a neurological disease 
• you have been in contact with someone with a flu-like illness and can start antiviral treatment within 36-48 hours
• you have not been effectively protected by vaccination.

You are not effectively protected by vaccination if you:

• have not been vaccinated since last winter
• cannot be vaccinated or have been vaccinated, but it hasn't taken effect yet (this can take up to two weeks)
• have been vaccinated against a form of flu virus that's different to the type going around.

If there is an outbreak of flu in a residential or nursing home – where the flu virus can often spread very quickly – antiviral medication may be offered to people if they have been in contact with someone with confirmed flu.

Source: NHS Choices.