What is influenza (flu)?
What do the names of influenza viruses mean?
How serious is influenza?
Who is most at risk?
What are the symptoms of influenza?
What is the normal incubation period for influenza?
When are patients infectious?
How is influenza spread?
What do you recommend for your patient who has influenza?
What precautions should patients take?
When does influenza occur?
How common is influenza?
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 influenza?
Is there anyone who should not be vaccinated?
Is there any medical treatment for influenza?
When is the best time to be vaccinated?
How does your patient 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 patients get influenza vaccine privately?
What is influenza (flu)?
Influenza is an acute viral infection of the respiratory tract. There are three types of influenza virus: A, B and C. Influenza A and influenza B are responsible for most clinical illness. Influenza is highly infectious with a usual incubation period of one to three days.
Influenza A is usually a more severe infection than influenza B. Influenza A subtypes exist which are named according to the haemagglutinin and neuraminidase antigens on the viral surface. Influenza C is an uncommon type that infequently causes infection.
What do the names of influenza viruses mean?
The names given to different types (‘strains’) of influenza 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 influenza 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, influenza is an unpleasant experience, but carries little danger. However, influenza can lead to other illnesses (‘complications’) because of the way it attacks the cells that line the respiratory tract – the nose and throat and the airways leading down into the lungs. Because it destroys cells in this protective lining, influenza 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 influenza can themselves be very dangerous and sometimes fatal even for young, fit patients – this is usually when a new form of the virus develops to which patients have no immunity.
Who is most at risk?
Influenza can be more dangerous and more likely to lead to other illness in certain groups of patients. Younger patients are more vulnerable because their immune systems have not previously encountered influenza viruses and therefore have not produced antibodies against them. Patients with an underlying illness such as chronic respiratory disease (asthma, chronic obstructive pulmonary disease), chronic heart or renal disease and diabetes mellitus are more likely to get serious complications from influenza. Older adults are more at risk because they may have a less effective immune system and are more likely to have underlying diseases.
Patients 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 should be given on an individual basis in the context of other clinical risk groups in a GP practice.
What are the symptoms of influenza?
The most common symptoms of influenza are an abrupt onset of fever, shivering, headache, muscle ache and dry cough. Many patients confuse influenza with other ‘influenza-like’ illnesses such as the common cold, which is caused by other respiratory viruses. However, cold symptoms are limited to the upper respiratory tract with runny nose, sneezing, watery eyes and throat irritation.
Cold symptoms usually occur gradually and do not cause a fever or body aches. Influenza affects both the upper and lower respiratory tract – the airways and the lungs – and causes a more widespread infection that the body has to work much harder to kill and repair. After the ‘acute’ phase of influenza is over (usually 3-5 days), tiredness, coughing and a general feeling of illness and weakness may continue for 1-2 weeks.
What is the normal incubation period for influenza?
2-3 days is the normal incubation period for influenza – the time taken from picking up the virus to becoming ill.
When are patients infectious?
Flu symptoms develop 1-4 days (2 days on average) after being infected. Patients with flu are usually infectious (can spread the virus) a day before symptoms start, and remain infectious for five or six days. Children and people with weaker immune systems (such as cancer patients) may remain infectious for slightly longer. People should try to avoid all unnecessary contact with others during this infectious period.
How is influenza spread?
The influenza virus is highly contagious and is easily passed from person to person when an infected person coughs or sneezes. One can pick up the influenza by touching a contaminated surface followed by touching one’s mouth, nose or eyes. The influenza 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 do you recommend for your patient who has influenza?
Advise rest, drinking plenty of fluids and taking analgesics. These help to keep the temperature down and relieve some of the discomfort. Influenza and influenza-like illnesses are normally self-limiting – the body deals with them in a few days. It is best to treat the infection at home until the patient is well enough to return to normal activities. Further 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 patients take?
Routine vaccination offers the best protection and patients 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 influenza 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 influenza?
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 (October to April in the UK). The number of patients 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 influenza who do not see their GP. This can increase considerably during an epidemic or pandemic.
What is an epidemic?
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. An epidemic is when the number of people getting the disease rises beyond the number usually expected. About 600 people a year die in the UK from seasonal flu. This rises to around 13,000 during an epidemic.
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 patients, influenza is not life-threatening, however unpleasant it may be. A bout of influenza 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?
Influenza 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 patients who have been vaccinated are protected from the strains of influenza in the vaccine. If a patient has been vaccinated and then contracts influenza, it is likely to be milder than if the patient had not been vaccinated.
Does the vaccine have any side-effects?
It is possible that a patient may get some swelling or redness where they 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 Summary of Product Characteristics for further information on side effects.
Can the vaccine cause influenza?
No. The vaccine cannot cause influenza because it doesn't contain live virus.
Is there anyone who should not be vaccinated?
The vaccine should not be given to a patient who has had a confirmed anaphylactic reaction to a pervious dose of vaccine or any component of the vaccine or has hypersensitivity to egg products.
If the patient has a high temperature on the day of the vaccination it is better to postpone it for a few days until the patient feels well.
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 September and early November, ready for the winter. The patient shouldn't wait until there is an influenza epidemic.
How does your patient go about getting vaccinated?
Some surgeries alert those who would benefit from vaccination in advance. Try to vaccinate as early in the autumn as possible. Most surgeries organise special vaccination sessions in the autumn and will arrange an appointment for those at risk then.
Does past infection with influenza make a patient immune?
To a certain extent the viruses that cause influenza frequently change, so patients who have been infected or given an influenza vaccination in previous years may become infected with a new strain. Because of this, and because any immunity produced by the influenza 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 influenza vaccination is regularly reviewed by an expert panel of the Joint Committee on Vaccination and Immunisation in the light of all relevant evidence.
Can patients get influenza vaccine privately?
If people outside the recommended ‘at risk’ groups wish to make arrangements and pay for an influenza vaccination privately, they should consult their healthcare professional for appropriate advice.