What is influenza (flu)?
Why does flu cause epidemics?
What do the names of flu viruses mean?
How serious is influenza?
Who is most at risk?
What are the symptoms of influenza?
When could I get ill?
When are people infectious?
How is influenza spread?
What should you do if you get flu?
What precautions should people take?
When does influenza occur?
How common is flu?
What is an epidemic?
What is a pandemic?
Who makes the decisions about the vaccine and vaccination?
Why not vaccinate everyone?
How effective is the vaccine?
Does the vaccine have any side-effects?
Can the vaccine cause flu?
Is there anyone who should not be vaccinated?
Is there any medical treatment for flu?
When is the best time to be vaccinated?
How do you go about getting vaccinated?
Does past infection with influenza make a person immune?
Is the age recommendation likely to be extended in the future?
Can people get flu vaccine privately?
What is influenza (flu)?
Influenza is a contagious, acute respiratory illness. It occurs all over the world and is responsible for a great deal of sickness and more than a million deaths each year. There are three main types of flu viruses, called A, B and C.
Influenza A is the most common and severe and causes epidemics and pandemics (widespread epidemics).
Influenza B generally causes less severe illness than A, although in children it can be as severe as influenza A and sometimes causes outbreaks of infection. Influenza B usually occurs along with the yearly outbreaks of influenza A.
Influenza C is the least common and causes milder illness, similar to a cold.
Why does flu cause epidemics?
The body defends itself against viruses by producing antibodies that target and attack the virus. Once it has produced these antibodies, it remembers how to make them and can quickly deal with that virus in the future and stop it at an early stage – this is what is called immunity.
Influenza viruses are continually changing and can therefore overcome immunity and remain infectious. These changes mean that the body may not have exactly the right antibodies available for complete immunity and so it has to produce a new set of antibodies to match the new set of viruses. Small changes happen all the time – this is called antigenic drift – and these changes don’t always completely overcome the body’s immunity. Influenza A undergoes the most rapid antigenic drift, which is why it causes the yearly flu outbreaks that we call ‘seasonal flu’.
However, sometimes a bigger virus change occurs, known as antigenic shift, and resulting in a new form of the virus being produced, which nobody has immunity to. Influenza A is the only type of influenza that does this, and it is what causes the widespread flu outbreaks called epidemics or even pandemics.
What do the names of flu viruses mean?
The names given to different types (‘strains’) of flu viruses are related to the area and year in which the new type was first found – names like ‘Asian flu 1957’, ‘Spanish flu 1918 or Swine flu H1N1 2009’. The serious antigenic shifts may first occur in flu viruses in animals or birds and then, in some cases, pass from one species to another, such as from birds or pigs to humans.
The medical system for identifying different Influenza A viruses is based on changes in two particular parts of the virus called H and N which are the antigens that the body uses to recognise the virus and develop the right antibodies. Examples look like this: A (H1N1), A (H1N2) and A (H3N2).
How serious is influenza?
For most healthy people, flu is an unpleasant experience, but carries little danger. However, flu can lead to other illnesses (‘complications’) because of the way it attacks the cells that line your respiratory tract – the nose and throat and the airways leading down into the lungs. Because it destroys cells in this protective lining, flu can cause other infections to develop – these may be caused by bacteria or other viruses and are called secondary infections.
Bronchitis and pneumonia are the most common complications, and these can be life threatening and require hospital treatment. Some very virulent forms of flu can themselves be very dangerous and sometimes fatal even for young, fit people – this is usually when a new form of the virus develops to which people have no immunity.
Who is most at risk?
Flu can be more dangerous and more likely to lead to other illness in certain groups of people. Younger people are more vulnerable because their immune systems have not previously encountered flu viruses and therefore have not produced antibodies against them.
People with an underlying illness such as chronic respiratory disease (asthma that requires continued or repeated use of inhaled or systemic steroids, chronic obstructive pulmonary disease), chronic heart or renal disease and diabetes mellitus or those with neurological conditions are more likely to get serious complications from flu. Older people are more at risk because they may have a less effective immune system and are more likely to have underlying diseases.
People who have a poorly functioning immune system are ‘immunocompromised’ or are ‘immunosuppressed’ by an immune-system disease or through treatment for another condition are more likely to be seriously affected by influenza or by secondary infections. Residents of nursing homes are at high risk of serious influenza complications for a variety of reasons. As they tend to be older, they are more likely to suffer from a chronic condition, which makes influenza more dangerous.
Health and social care staff and those people who are in receipt of a carer's allowence or are the main carer of an elderly or disabled person may also be at risk. Vaccination is at the descretion of your GP, and based on individual clinical risk, you should consult your GP or nurse to receive the appropriate advice.
What are the symptoms of influenza?
The most common symptoms of flu are a sudden onset of fever, chills, headache, muscle ache and dry cough. Many people confuse influenza with the symptoms of the common cold. However, cold symptoms usually occur gradually and do not cause a fever or body aches. Influenza symptoms are more severe making you unable t do your usual activities. Influenza symptoms will usually peak after 2-3 days and you should feel better within 5-8 days. A general feeling of tiredness and cough may continue for 1-2 weeks.
When could I get ill?
2-3 days is the normal ‘incubation period’ for flu – the time taken from picking up the virus to becoming ill.
When are people infectious?
People are usually infectious for 1 day before their symptoms start, then for about 3-5 days after that, but sometimes this can be as long as 10 days. Children can remain infectious for up to 2 weeks, and severely immunocompromised people for several weeks.
How is influenza spread?
The flu virus is highly contagious and is easily passed from person to person when an infected person coughs or sneezes. Touching a contaminated surface followed by your mouth, nose or eyes can pick up flu. The flu virus can live on a hard surface such as a doorknob for up to 24 hours and on a soft surface for around 20 minutes. Catching coughs and sneezes in a tissue and throwing it away helps prevent the spread.
What should you do if you get flu?
Rest, drink plenty of fluids and take analgesics. These help to keep your temperature down and relieve some of the discomfort. Flu and flu-like illnesses are normally self-limiting – the body deals with them in a few days. It is best to treat your infection at home until you are well enough to return to normal activities. Medical advice should be sought if symptoms become severe or last more than about a week. Those with chronic or long-standing illness may need medical attention earlier.
What precautions should people take?
Routine vaccination offers the best protection and people who are at high risk of infection should be vaccinated. It is difficult to avoid infection if there is an epidemic. Keeping away from crowded places can reduce the risk of becoming infected and spreading it to others. A previous flu infection or vaccination will not necessarily provide protection against further infections because the virus is continually changing and different types of the virus circulate each winter.
When does influenza occur?
Influenza occurs most often in the winter months and usually peaks between December and March in the northern hemisphere. Illnesses resembling influenza may occur in the summer months but they are usually due to other viruses.
In temperate climates influenza strikes from late autumn through to spring, although technically influenza is not bound by seasons, and can occur all year round in tropical climates.
How common is flu?
Worldwide, 20% of children and 5% of adults develop influenza each year. Up to 15% of the population may develop influenza in any one year.
Seasonal flu is a very common illness that occurs every year, usually during the winter months (September to April in the UK). The number of people who consult their GP with flu-like symptoms varies from year to year, but is usually between 50 and 200 for every 100,000 people. This is in addition to the many people with flu who do not see their GP. This can increase considerably during an epidemic or pandemic.
What is an epidemic?
An epidemic is when the number of people getting the disease rises beyond the number usually expected – in the UK this is when more than 200 per 100,000 of the population report flu to their GP.
What is a pandemic?
A pandemic is a worldwide epidemic of a disease. It does not necessarily mean mass fatalities. A pandemic refers to how far across the globe the disease has spread, rather than its severity, and as such a pandemic can result in a low fatality count. It may start mild and become severe, or vice versa. It may also start mild and stay that way, or start severe and stay severe.
Who makes the decisions about the vaccine and vaccination?
The World Health Organization advises on the strains that the vaccine should contain depending on which ones are expected to circulate in the coming season. The Chief Medical Officer who is advised by an expert statutory group, the Joint Committee on Vaccination and Immunisation (JCVI), gives advice on who should actually be offered the vaccine in the UK each year.
Why not vaccinate everyone?
For the majority of people flu is not life-threatening, however unpleasant it may be. A bout of flu offers long-term protection against the same and closely related strains of influenza. It is the 'at risk' groups who benefit most from vaccination.
How effective is the vaccine?
Flu vaccinations prevent about 70-80% of influenza in healthy adults when the match between the vaccine and circulating strains is close. In recent years we have been getting better at predicting the strains, which are likely to circulate.
Most people who have been vaccinated are protected from the strains of flu in the vaccine. If you have been vaccinated and then contract flu it is likely to be milder than if you had not been vaccinated.
Does the vaccine have any side-effects?
It is possible that you may get some swelling or redness where you were injected or a mild fever, aching muscles or headache, but this should only last for one to two days. People who have certain allergies may also be affected by the vaccine.
Flu vaccines from different manufacturers may differ from one another - please refer to the relevant Patient Information Leaflet for further information on side effects.
Can the vaccine cause flu?
No. The vaccine cannot cause flu because it doesn't contain live virus.
Is there anyone who should not be vaccinated?
Flu vaccine contains only inactivated virus particles, which cannot cause you to have flu. Your body reacts to these particles by producing antibodies, and this may cause a slight temperature and some aching muscles, and you may have slight soreness at the injection site.
Anyone who has had a confirmed anaphylactic reaction to a previous dose of vaccine or any component of the vaccine or if you have a hypersensitivity to egg products should not be vaccinated. Please consult your GP or nurse if you have any concerns. If you happen to have a high temperature on the day of your vaccination it is better to postpone it for a few days until you feel well.
Not all flu vaccines are suitable for all age groups so your GP will choose the correct vaccines for you.
Is there any medical treatment for flu?
There are now antiviral drugs available for the treatment and prevention of influenza. During the 2009/2010 season, they were recommended for all clinically diagnosed cases of influenza. Once the peak was over though, they were only recommended for patients ‘at risk’ of developing more serious complications. These included the elderly or those with, for example, asthma or heart disease and patients with chronic neurological conditions or chronic liver disease. Treatment should be started within 48 hours of the onset of symptoms.
Antivirals should therefore be used when: a person with a flu-like illness is in an ‘at risk’ group and they can start treatment within 48 hours (or within 36 hours for zanamivir treatment in children) of the onset of symptoms as per licensed indications and the national surveillance schemes indicate that influenza virus A or B is circulating.
When is the best time to be vaccinated?
The best time to be vaccinated is between late September and early November, ready for the winter. You shouldn't wait until there is a flu epidemic.
How do you go about getting vaccinated?
If you think you need a flu vaccination, check with your doctor or the practice nurse – or if a nurse visits you regularly, ask them. Try to do so as early in the autumn as possible. Most doctors surgeries organise special vaccination sessions in the autumn and will arrange an appointment for you then.
Does past infection with influenza make a person immune?
To a certain extent the viruses that cause flu frequently change, so people who have been infected or given a flu vaccination in previous years may become infected with a new strain. Because of this, and because any immunity produced by the flu jab may decrease over the year after vaccination, it is recommended to be vaccinated every year.
Is the age recommendation likely to be extended in the future?
The current recommendations are based on existing evidence, which shows clear benefits for those in the 'at risk' groups. The Department of Health’s policy on flu vaccination is regularly reviewed by an expert panel of the Joint Committee on Vaccination and Immunisation in the light of all relevant evidence.
Can people get flu vaccine privately?
If people outside the recommended ‘at risk’ groups wish to make arrangements and pay for a flu vaccination privately, they should consult their GP who will give them the appropriate advice.
