Published by Bupa's Health Information Team, February 2011.

This factsheet is for people who have seasonal flu, or who would like information about it.

Flu (or influenza) is caused by flu viruses. Seasonal flu follows a pattern and tends to occur at around the same time every year. Most people fight off the infection without medical treatment.

About flu
Symptoms of flu
Complications of flu
Causes of flu
Diagnosis of flu
Treatment of flu
Prevention of flu  

About flu

Seasonal flu is caused by a virus. Flu viruses can infect your nose, throat, sinuses and lungs.

There are three main types of flu virus: type A, type B and type C. Type A is the most common and the most infectious, and usually causes the most severe symptoms. Type B usually causes less serious symptoms and type C usually causes a mild infection similar to the common cold.

Flu viruses change from year to year. Every few years the flu virus changes a lot, which may cause an epidemic. This means that a lot of people become infected because very few people have immunity to the new virus. Sometimes a new virus can cause a pandemic, which means that the virus spreads quickly throughout the world, infecting large numbers of people.

Most people recover from flu after a few days or weeks. However, for older people, newborn babies and people with other health problems, for example heart disease or chest problems, flu can be more serious.

Symptoms of flu

When you catch flu from someone, it usually takes two to three days for your symptoms to start. Flu viruses grow in the soft, warm surfaces of your nose, throat, sinuses, airways and lungs, so this is where you usually get symptoms. These can include:

  • fever (a high temperature, usually between 38ºC and 40ºC)
  • a blocked or runny nose
  • sneezing
  • headache
  • sore throat
  • cough
  • chills
  • aching muscles
  • feeling tired

Symptoms usually last for about a week but you may feel tired for a few weeks. If your child has flu he or she may also feel sick or be sick and have diarrhoea.

Complications of flu

Most healthy adults recover completely from flu within a few weeks. However, young children, people over the age of 65 and those with other health problems are more likely to have complications from flu, which can include:

  • conditions that affect the lungs, for example, pneumonia and bronchitis
  • worsening of chest conditions such as asthma
  • middle ear infection
  • inflamed sinuses (sinusitis)

Young children can sometimes have seizures or fits, called febrile convulsions, because of their high body temperature.

You're at greater risk of having complications from flu if you're over 65, or if you have:

  • asthma
  • a long-term lung condition such as chronic obstructive pulmonary disease
  • diabetes, which you take medication for (insulin-dependent diabetes)
  • heart disease
  • kidney disease
  • liver disease
  • had a stroke
  • a weakened immune system, for example, if you have HIV/AIDS or are taking medicines that suppress the immune system


Causes of flu

Flu viruses are very infectious. Most people catch flu by breathing in air that has the virus in it. This usually happens when people with flu cough or sneeze, which spreads the virus in droplets in the air.

You can also catch flu by direct contact with someone who has it, for example by shaking hands or by touching something they have recently touched. You pick up the flu virus on your hands and then when you touch your nose or mouth you may pass the virus onto yourself. The flu virus can live on a hard surface for up to 24 hours and on a soft surface for about 20 minutes.

You're infectious and can spread the virus to other people when your symptoms start, and for five days afterwards. Children are infectious for longer.

Diagnosis of flu

Most people are able to diagnose themselves as having flu and won't need to see a doctor. However, if your symptoms get worse or if your fever and aching muscles last longer than a week, you should see a doctor. You should also see a doctor if you have a medical condition which may make flu worse.

Your doctor will ask you about your symptoms and examine you. He or she may also ask you about your medical history. Your doctor will diagnose flu from your symptoms. No other tests are usually needed.

Treatment of flu



There is no cure for flu. However, there are things you can do to make yourself more comfortable including the following.

  • Drinking enough fluids to prevent dehydration – six to eight glasses a day.
  • Using steam inhalations with menthol, salt water nasal sprays or drops may be helpful.
  • Vapour rubs may help relieve symptoms for children.
  • Drinking hot drinks (particularly with lemon), hot soups or spicy foods can help to ease irritation and pain in your throat and help reduce congestion.
  • Sucking sweets or lozenges which contain menthol or eucalyptus may sooth your throat.
  • Gargling with salt water may help a sore throat.
  • Resting – you may need to stay off work or school for up to a week.



If you have muscle pains, a headache, sinus pain or a sore throat then you can take paracetamol (acetaminophen) or non-steroidal anti-inflammatory medicines, such as ibuprofen, as a painkiller. These medicines will also help to reduce a fever if you have one.

It's important to check the dose you're taking of different types of medicines. It's easy to accidentally have more than the daily dose by using more than one product, for example tablets, capsules and a hot lemon drink that contain the same active ingredient, such as paracetamol.

Children can take paracetamol and ibuprofen as a liquid. Children under the age of 16 should not take aspirin. Talk to a pharmacist about which painkillers are suitable for your child.

If you have a blocked nose or sinuses then a decongestant may help to ease the symptoms. Nasal sprays can give you relief from a blocked nose for a few hours. Decongestant tablets may also help to ease the symptoms of blocked sinuses. However, you shouldn't take decongestants for too long as they can cause rebound congestion. Decongestants shouldn't be given to children under the age of six. If you have high blood pressure or problems with your liver or kidneys, you should talk to a doctor before you take decongestants.

Always read the patient information leaflet that comes with your medicine and if you have any questions, ask a pharmacist for advice.

Antibiotics aren't used to treat infections caused by a virus. A doctor may prescribe antibiotics if you develop a secondary infection caused by bacteria, such as a chest infection or an ear infection.
If you're over the age of 65 or have other health problems which may increase your risk of complications, a doctor may prescribe an antiviral medicine. Antiviral medicines can reduce the length of time your symptoms last by around one day.

However, you need to start taking antiviral medicines within two days of getting the flu. These medicines can be taken as tablets or as an inhaler (similar to the ones used for asthma).

Availability and use of different treatments may vary from country to country. Ask a pharmacist or doctor for advice on your treatment options.

Complementary medicines

There are a number of supplements and complementary medicines that are popular for treating colds. These include vitamin C, menthol, zinc, garlic and Echinacea. There is not enough evidence to suggest that taking these or Chinese herbal medicines are likely to be effective at treating flu.

Menthol can help to ease a blocked nose because it has a cooling sensation. It can also help to relieve the symptoms of a sore throat and cough because it contains a local anaesthetic which numbs the area.

Complementary medicines can interact with other medicines, so you should always tell your doctor or pharmacist about all of the medicines you're taking.

Prevention of flu

If you have flu you can help to prevent it from spreading to other people by:

  • covering your nose and mouth when coughing or sneezing, and using a tissue when possible
  • throwing away tissues straight after you have used them
  • maintaining good basic hygiene, for example, washing hands frequently with soap and water to reduce the spread of the virus from your hands to your face or other people
  • using household cleaning products to clean surfaces such as door handles
  • keeping away from other people as much as you can while you're ill

You may also be able to prevent yourself getting flu by being vaccinated against it. Check whether flu vaccines are available in your country.

You may benefit from having the flu vaccine if you have:

  • chest conditions, including asthma
  • long-term heart, brain, liver or kidney disease
  • diabetes
  • a weakened immune system, for example if you have HIV/AIDS, or are taking medicines that affect your immune system

You may also benefit from having the flu vaccine if:

  • you're over 65 and at risk of developing complications from flu
  • you live in a care home or residential home
  • you're the main carer for someone
  • you live with someone who has a weakened immune system
  • you're a healthcare worker and have contact with patients


This section contains answers to common questions about this topic. Questions have been suggested by health professionals, website feedback and requests via email.
How is seasonal flu different from bird flu and swine flu?
Is there anyone who shouldn’t have the flu vaccine?
I had the flu vaccine yesterday and have had a headache and temperature since then – is it possible the vaccine has given me flu? 

How is seasonal flu different from bird flu and swine flu?

Seasonal flu is a virus that affects people and happens around the same time every year. Bird flu usually only infects birds and swine flu usually only affects pigs. However, these types of flu can sometimes be passed on to people. 


Avian flu (bird flu) usually only affects birds. In some birds it doesn’t cause any problems, but in poultry, such as chickens, it can spread quickly and kill large numbers of birds. Sometimes the avian flu virus can spread to people, usually those who work in close contact with poultry. However, it’s very unlikely that the virus will spread from person to person.  
Swine flu is a virus that usually causes illness in pigs. People don’t normally get swine flu, but human infections can and do happen. In 2009 there was a swine flu pandemic where many people became infected with the swine flu virus.
Seasonal flu is an illness caused by a flu virus which affects people. Seasonal flu viruses are spread easily from person to person in droplets in the air. Seasonal flu occurs regularly every year.

Is there anyone who shouldn’t have the flu vaccine?

Almost everyone is able to be vaccinated against seasonal flu. However, if you have had an allergic reaction to the vaccine before, or are severely allergic to egg you shouldn’t have the vaccine.


Some flu vaccines are made by placing the virus into a hen's egg where it's left to grow before being killed and purified. Therefore, although the vaccine doesn't have egg in it, it may have been contaminated with part of the egg. If you have a severe egg allergy that means you need urgent treatment if you come into contact with egg, your GP may advise you not to have the flu vaccine.
If you have had a severe reaction to the vaccine before, or are allergic to any of the ingredients used to make the vaccine, then your GP may also suggest that you don’t have the vaccine.

I had the flu vaccine yesterday and have had a headache and temperature since then – is it possible the vaccine has given me flu?

You can't get flu from the flu vaccine. However, some people do have side-effects after being vaccinated, which are similar to the symptoms of flu.


The vaccine for seasonal flu doesn’t contain any live viruses so you can’t get infected with flu from the vaccine.
The vaccine can sometimes cause side-effects. These are similar to some of the symptoms of flu. You may develop a headache, aching muscles and a mild fever after your vaccination. You may also have some pain, redness and swelling where the infection was given. These symptoms usually disappear after a day or two.
If you need pain relief, you can take over-the-counter painkillers such as paracetamol or ibuprofen. Always read the patient information that comes with your medicine and if you have any questions, ask your pharmacist for advice.

Further information



  • Seasonal influenza. Clinical Knowledge Summaries., published August 2009
  • Influenza factsheet. Health Protection Agency., published January 2010
  • Influenza frequently asked questions. Health Protection Agency., published April 2010
  • Influenza. BMJ Clinical Evidence., published March 2009
  • Common cold medications. Cardiff University., accessed 29 September 2010
  • Joint Formulary Committee, British National Formulary. 60th ed. London: British Medical Association and Royal Pharmaceutical Society of Great Britain; 2010: 257
  • Amantadine, oseltamivir and zanamivir for the treatment of influenza. National Institute for Health and Clinical Excellence (NICE), published 2009.
  • Chen XY, Wu T, Liu GJ et al. Chinese medicinal herbs for influenza. Cochrane Database of Systematic Reviews 2005, Issue 4. doi: 10.1002/14651858.CD004559.pub3
  • Simon C, Everitt H, Kendrick T. Oxford handbook of general practice. 2nd ed. Oxford: Oxford University Press, 2007:490 
  • Avian flu. Health Protection Agency., published August 2008
  • Swine flu: frequently asked questions. Health Protection Agency., published March 2010
  • Immunisation against infectious disease. Department of Health., published September 2010


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Published by Bupa’s Health Information Team, February 2011.

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