| ||||||||||||||||||||||||||||||||||||||||||||||||||||
Influenza and its prevention
Executive Editor, InnovAiT
Research Fellow and General Practitioner, University of Southampton, UK
E-mail: chantal.simon{at}oxfordjournals.org
E-mail: ohgp123{at}aol.co.uk
 |
Abstract |
|---|
 TOP Abstract The GP curriculum and...Presentation of influenzaManagementProphylaxis with antiviralsInfluenza vaccinationReferences |
|---|
Influenza is a respiratory illness caused by the influenza virus. Most cases in the UK occur in a 6- to 8-week period during the winter. The exact timing of this period, number of people affected and severity of the illness varies from year to year.
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 and spreads rapidly, especially in closed communities such as nursing homes. It is passed on through droplet spread, person-to-person contact or contact with contaminated items. It has an incubation period of 1–3 days. The infectious period varies but an infected person can pass on the disease from the day before symptoms appear for a period of 3–5 days.
Influenza activity is monitored in the UK with virological surveillance together with reports of new consultations for influenza-like illness from sentinel GP practices (Fig. 1). During epidemics GP consultation rates rise considerably. The highest recorded consultation rates were for the 1989–90 epidemic when there were 583 consultations per 100 000 population per week in England and Wales and 1184 consultations per 100 000 population per week in Scotland. This compares with a baseline rate of about 5 consultations per 100 000 population per week for the rest of the year.
|
In winters when incidence is low, it is estimated that influenza is responsible for 3000–4000 deaths across England and Wales. During severe epidemics, like those recorded in 1975–76 and 1989–90, the death rate rises significantly. These two epidemics resulted in an estimated 29 646 and 23 046 deaths, respectively. Serious illness and mortality from influenza is highest among neonates, older people and those with underlying disease, particularly chronic respiratory and cardiac disease, or those who are immunosuppressed.
As influenza is such a major health problem, it is a Government priority to vaccinate high-risk groups to prevent the disease. In England, 75% of those over 65 years of age were given influenza vaccination between October 2005 and January 2006 and prevention of respiratory infection by immunization of at-risk groups with annual influenza vaccination is a major challenge for most practices. This article aims to describe the presentation and treatment of influenza and its prevention in the community.
Statement 5 of the GP curriculum (healthy people: promoting health and preventing disease) requires GPs in training to be able to:
Statement 15.8 of the GP curriculum (respiratory problems) requires GPs in training to develop a knowledge base which includes knowledge of the epidemiology, presentation, management and treatment of lower respiratory tract infections including influenza. It also requires GPs in training to know about vaccination against influenza infection.
|
|
Presentation of influenza |
|---|
|
TOPAbstractThe GP curriculum and...Presentation of influenzaManagementProphylaxis with antiviralsInfluenza vaccinationReferences |
|---|
Severity of the illness varies enormously. Serological studies in health care professionals show that between 30% and 50% of influenza infections in healthy individuals are asymptomatic. In mild cases, symptoms are like those of a common cold. In more severe cases, fever begins suddenly accompanied by prostration and generalized aches and pains. Other symptoms may follow headache, sore throat and respiratory tract symptoms (usually cough and/or coryza). Acute symptoms resolve in 2–7 days but weakness, sweating and fatigue may persist longer.
Primary pneumonia due to influenza virus is usually caused by influenza A, but is rare. It may affect previously healthy individuals but patients with underlying disease, such as those with chronic obstructive pulmonary disease, are at greater risk. Influenza pneumonia develops rapidly and presents with progressive dyspnoea. It has a high mortality rate. However, the most common cause of pneumonia during influenza epidemics is secondary bacterial infection, usually with Staphylococcus aureus or Staphylococcus pneumococcus. Rarely severe influenza may be complicated meningitis or encephalitis.
|
Management |
|---|
|
TOPAbstractThe GP curriculum and...Presentation of influenzaManagementProphylaxis with antiviralsInfluenza vaccinationReferences |
|---|
In general, management is symptomatic with rest, fluids and paracetamol for fever and symptom control. Secondary infections, such as chest infection, otitis media or tonsillitis, may require treatment with antibiotics. Exacerbations of asthma or chronic obstructive pulmonary disease due to influenza also require treatment.
Antivirals are not a cure but may shorten the duration of symptoms and reduce incidence of complications if they are started within 48 hours of the onset of symptoms. Two antivirals are available in the UK. Zanamivir (Relenza®) is taken by inhalation at a dose of 10 mg twice daily for 5 days and should only be used for adults. It can cause bronchospasm, so ensure that a short-acting bronchodilator is available if the patient has a tendency to bronchospasm and avoid prescribing in the community if the patient has severe asthma. Oseltamivir (Tamiflu®) is taken by mouth at an adult dose of 75 mg twice daily for 5 days. It can also be used at a reduced dose for children over the age of a year.
Antivirals should only be sued for treatment of non-pregnant patients in high-risk groups (Table 1) and only when influenza is prevalent in the community.
|
|
Prophylaxis with antivirals |
|---|
|
TOPAbstractThe GP curriculum and...Presentation of influenzaManagementProphylaxis with antiviralsInfluenza vaccinationReferences |
|---|
Oseltamivir is recommended for prophylaxis in high-risk patients over the age of 13 years who are not effectively vaccinated or who live in residential care where a staff member has influenza-like symptoms, but only when influenza is prevalent in the community. It is taken at a dose of 75 mg per day for a period of 7–10 days from the date of diagnosis of the latest case in the establishment.
|
Influenza vaccination |
|---|
|
TOPAbstractThe GP curriculum and...Presentation of influenzaManagementProphylaxis with antiviralsInfluenza vaccinationReferences |
|---|
The influenza virus (Fig. 2) has two principal surface antigens: haemagglutinin (H) and neuraminidase (N). It is these surface antigens that promote the immune response that protects individuals from future infection. Unfortunately, influenza surface antigens are not constant and change over time in two ways.
|
Antigenic drift is a term describing the minor changes (due to point mutations in the genome) that occur progressively from year to year. These changes affect both influenza A and influenza B viruses, but influenza A changes more rapidly than influenza B.
Antigenic shift only affects influenza A viruses. It occurs when a whole segment of the genome is replaced, usually affecting the ‘H’ surface antigen, resulting in the emergence of a new subtype of influenza A. The most widely accepted theory explaining this antigen shift is that the segments come from animal influenza viruses. A new subtype can cause widespread epidemics or even a pandemic if populations have little or no immunity.
Three influenza pandemics have occurred in the last century: ‘Spanish flu’ affected large parts of the world population and is thought to have killed at least 40 million people, mainly healthy young adults, in 1918–19; ‘Asian flu’ caused a pandemic in 1957 and ‘Hong Kong flu’ caused another pandemic in 1968. Most recently, limited outbreaks of a new influenza subtype A (H5N1) directly transmitted from birds to humans (bird flu) have occurred. There is no firm evidence that H5N1 has acquired the ability to pass easily from person to person but concern remains that the virus might develop the ability to pass from person to person or that it might mix with human flu viruses to create a new virus and create a new human flu pandemic.
Influenza vaccination aims to prevent influenza. Influenza vaccines are trivalent containing two subtypes of influenza A virus and one subtype of influenza B. Due to the changing nature of the influenza viruses, the World Health Organization (WHO) monitors influenza viruses throughout the world. Each year the WHO makes recommendations about the strains that will be prevalent the following winter and influenza vaccines are formulated using virus strains in line with those recommendations. To ensure continuing protection, annual immunization with vaccine against the currently prevalent strains is necessary. As influenza activity is not usually significant before mid-November, the ideal time for immunization is between September and early November in the UK. If a new subtype of influenza A with pandemic potential emerges, a monovalent vaccine against that particular strain might be issued.
In the manufacture of influenza vaccinations, the viruses are grown in embryonated hens’ eggs, chemically inactivated and then further treated and purified. Influenza vaccines are supplied as suspensions of vaccines in pre-filled syringes for injection. As the vaccines do not contain live organisms, they cannot cause influenza. Vaccines should be stored in the original packaging at +2°C to +8°C and protected from light. Failure to do this can result in reduced efficacy.
Administration
At present, influenza vaccination is routinely offered every year to health care professionals, carers and patients at high risk of complications from influenza (Box 1). Before giving influenza vaccination, shake the pre-filled syringe well. Give the vaccine by intramuscular injection into the upper arm or anterolateral thigh, except for patients with bleeding disorders who should receive the vaccine by deep subcutaneous injection to reduce the risk of bleeding. The dosage and schedule are summarized in Table 2. Influenza vaccine can be given at the same time as other vaccines but should be given at a separate site (at least 2.5 cm apart from the other vaccination) and preferably in a different limb. The date of vaccination, site of vaccination and batch number of the vaccine should be recorded in the patient notes.
Box 1. Target groups for influenza vaccination
|
|
Vaccination provides those immunized with 77% protection (range 30–90%) against the strains present in the vaccine, with antibodies reaching protective levels 10–14 days after vaccination. Immunization has been shown to reduce the incidence of pneumonia, hospital admissions and mortality. It is important to stress to patients vaccinated that many other organisms cause respiratory infections similar to influenza during the influenza season. Influenza vaccine will not protect against these diseases.
Common side effects
Common local side effects include pain, swelling or redness at the injection site. Less commonly a small painless nodule will form. These side effects should resolve spontaneously within a few days. More generalized side effects such as a low-grade fever, malaise, shivering, fatigue, headache, myalgia and arthralgia are also common. Advise patients that these symptoms are also likely to resolve within a few days and to take paracetamol for symptom control meanwhile.
Contraindications
There are very few contraindications to influenza vaccination. Vaccination should not be given to those who have had
- a confirmed anaphylactic reaction to a previous dose of the vaccine,
- a confirmed anaphylactic reaction to any component of the vaccine (neomycin, kanamycin, gentamicin, polymyxin B or thiomersal) or
- a confirmed anaphylactic hypersensitivity to egg products as the vaccines are prepared in hens’ eggs.
Influenza immunizations for at-risk groups as a directed enhanced service
This directed enhanced service aims to provide influenza vaccination for the elderly and other ‘at-risk’ groups (Box 1). Those providing the service are paid for doing so in addition to their global sum payment. Practices do not have preferred provider status for the annual influenza vaccination programme but most GP practices do provide this service. To provide this service
- Practices are expected to use a call–recall system identifying those at-risk through existing registers compiled for use within the Quality and Outcomes Framework (QOF)
- Practices not participating in the QOF must compile a register to qualify to provide this enhanced service
Organization of influenza vaccination programmes in primary care
GP practices do not have preferred provider status. The precise organization will vary from practice to practice. Practices usually order their vaccines almost as soon as the previous year's vaccination programme has finished. Vaccines are delivered to the practice in September or early October. On arrival of the vaccine, the practice usually advertises that the annual flu campaign is about to start, for example through notices in the waiting room (Fig. 3), notices on the practice website and printed reminders on the facing pages of electronically generated prescriptions. Many practices also send reminders to eligible patients to come in for their flu vaccinations.
|
Most practices give the bulk of their vaccinations in special flu clinics. These may be within normal practice hours but many practices schedule these for evenings or Saturday mornings to prevent the large numbers of patients coming for influenza vaccination disrupting other practice activities. Patients are often invited to attend in batches, for example alphabetically based on surname, to spread the workload. On arrival, they are advised to roll up one sleeve ready for vaccination. In this way, many people can be vaccinated within a short period of time. Increased vaccination rates in the surgery can be achieved if vaccination is also given opportunistically, for example to those falling into the target groups for influenza vaccination who attend the surgery for other reasons.
House-bound individuals and those in residential care should not be forgotten. The list of patients unable to attend the surgery should be reviewed. Often residential care homes have a member of staff able to give the vaccinations, or will arrange for a member of the community nursing staff to come in to give every resident a vaccination on the same day. Some already in contact with the community nursing services or who are likely to see a GP can be vaccinated opportunistically. Others will need visits specifically to administer their vaccinations. Depending on local arrangements this may be done by a member of the practice nursing team or the community nursing team.
Influenza vaccination and the QOF
QOF points are awarded for vaccinating high proportions of at-risk patients against influenza. They include patients with diabetes, coronary heart disease, stroke or transient ischaemic attack and chronic obstructive pulmonary disease. Targets and points available are summarized in Table 3.
|
Key points
|
|
References |
|---|
|
TOPAbstractThe GP curriculum and...Presentation of influenzaManagementProphylaxis with antiviralsInfluenza vaccinationReferences |
|---|
-
British National Formulary. (September 2007) (Issue 54). Available from: www.bnf.org/bnf/ [date last accessed 16.12.2007].
Chief Medical Officer. Explaining pandemic flu (2005) Available from: www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/@dh/@en/documents/digitalasset/dh_4121749.pdf [date last accessed 16.12.2007].
Department of Health. Immunisation against infectious disease—the Green Book (2006) Available from: www.dh.gov.uk/en/Policyandguidance/Healthandsocialcaretopics/Greenbook/DH_4097254 [date last accessed 16.12.2007].
Health Protection Agency. Topics A-Z: Influenza. Available from: www.hpa.org.uk/infections/topics_az/influenza/default.htm. [date last accessed 16.12.2007].
Lynch J, Simon C. Oxford GP Library: respiratory problems (2007) OxfordOxford University Press ISBN 9780198571377.
NICE. Guidance on the use of zanamivir, oseltamivir and amantadine for the treatment of influenza (2003) Available from: www.nice.org.uk/nicemedia/pdf/58flua4summary.pdf [date last accessed 16.12.2007].
RCGP Curriculum. Statement number 5: Healthy people: promoting health and preventing disease. Available from: www.rcgp-curriculum.org.uk/PDF/curr_5_Healthy_people.pdf [date last accessed 16.12.2007].
RCGP Curriculum. Statement number 15.8: Respiratory problems. Available from: www.rcgp-curriculum.org.uk/extras/curriculum/statementDetails.aspx?id=30 [date last accessed 16.12.2007].
The Information Centre for Health and Social Care. Immunisation statistics (2005/6) Available from: www.ic.nhs.uk/statistics-and-data-collections/health-and-lifestyles/immunisation/immunisation-statistics-england-2005-2006 [date last accessed 16.12.2007].
UK Clinical Virology Network. Available from: www.clinical-virology.org/ [date last accessed 16.12.2007].
World Health Organization. Influenza. Available from: www.who.int/csr/disease/influenza/en/ [date last accessed 16.12.2007].
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||