Seasonal flu

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, including symptoms and causes.

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 seasonal 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.

In the UK you’re most likely to get seasonal flu in the autumn and winter months, between October and April.

Symptoms of seasonal 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 seasonal 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 seasonal 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 seasonal flu

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

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

Treatment of seasonal flu

Self-help

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.
• Steam inhalations with menthol, salt water nasal sprays or drops may be helpful.
• Vapour rubs may help relieve symptoms for children.
• 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.

Medicines

If you have muscle pains, a headache, sinus pain or a sore throat then you can take paracetamol or 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 your 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 your GP before you take decongestants.

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

Antibiotics aren’t used to treat infections caused by a virus. Your GP 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, your 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).

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 seasonal 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. Every year new flu vaccines are made from the three viruses that are most likely to cause flu that winter. The flu vaccine should provide you with protection against seasonal flu for one year. However, the vaccine isn’t always effective in everyone.

The flu vaccine is available to everyone over 65 and is given to people at risk of developing complications from flu. This includes adults and children (over six months) who 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

Your GP may also suggest that you have the flu vaccine if:

• 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

If you’re due to have a flu vaccination you will be asked to visit your GP surgery every year between September and early November. Talk to your GP or nurse if you would like more information.

For answers to frequently asked questions on this topic, see FAQs.

For sources and links to further information, see Resources.