5.1 Introduction

Influenza is a viral illness characterised by headache, fever, cough, sore throat and aching muscles. Although unpleasant it is usually a self limiting illness with recovery in 2-7 days. Complications can occur as a result of influenza infection including otitis media, bronchitis and pneumonia. The young and old are particularly vulnerable to influenza in whom the condition may cause death as a result of the complications. The virus that causes influenza was first identified in 1933. There are three types of influenza virus: A, B and C. Type A normally causes a more serious illness than types B and C. There are three categories of influenza for surveillance purposes: seasonal, pandemic and avian influenza ^{(1, 6)}. This chapter is going to describe some of the surveillance systems used to monitor seasonal influenza at local, regional, national and international levels and present some of the recent seasonal surveillance information.

5.2 Seasonal Influenza

Seasonal influenza usually occurs between December and March in the United Kingdom. There are a number of different surveillance systems that give us information regarding seasonal influenza via syndromic surveillance: Royal College of General Practitioners spotter practices, QFLU, NHS Direct and Medical Officers for Schools Association. Syndromic surveillance is based upon symptoms and not upon confirmed diagnoses. Other surveillance information can be obtained from the uptake of influenza vaccine and laboratory reporting of isolates obtained from specimens taken from infected individuals. Weekly summaries of influenza surveillance are produced by the Health Protection Agency during the seasonal influenza season at national and regional levels. Seasonal influenza surveillance also occurs in Europe through the European Influenza Surveillance Scheme ⁽⁵⁾, and internationally coordinated by the World Health Organisation ⁽¹⁷⁾. Some of the British based schemes will now be discussed in more detail. 

5.3 Royal College of General Practitioners

The Royal College of General Practitioners sentinel surveillance system was established in 1957. It now consists of approximately 100 GP practices spread across England and Wales who submit data to the Research Unit located in Birmingham, established in 1964, through the Weekly Returns Service. Patient information is anonymised and based upon well recognised Read codes. The baseline threshold rate, currently 30 per 100 000 persons, is based upon the weekly consultation rate for new episodes of influenza and influenza like illness. The National Institute for Health and Clinical Excellence (NICE) utilise this baseline in their guidance surrounding the usage of antivirals for the treatment of influenza ⁽¹¹⁾. The advantage of this system is that many years of historical data is available for analysis and comparisons. Information about other conditions is also collected to provide valuable insight into health trends in Primary Care.

Table 5.1: Number of GP practices participating in QFLU in the West Midlands

Figure 5.1: RCGP data consultation rates for influenza like illness per 100 000 from 1968-2007

RCGP data consultation rates for influenza like illness per 100 000 from 1968-2007

5.4 QFLU

This is a surveillance system based upon General Practitioners EMIS computer systems (the main supplier of GP computer systems in the England). It was developed by EMIS and Nottingham University. QFLU covers approximately 3,300 GP practices and a population of 25.5 million, although this figure varies on a weekly basis due to differing levels of practice participation. It is the largest surveillance system of its type in Europe. Data upon consultations for influenza like illness are automatically extracted from participating practices on a weekly basis and collated by Nottingham University. This information is sent to West Midlands Regional Surveillance Unit where analysis takes place and consultation rates for influenza like illness are calculated for the region. The advantage of Q-Flu is that it covers a large population and rates can be calculated down to a PCT level and prescribing data e.g. use of antivirals can be described. During a pandemic the QFLU system has the capacity to report daily consultation rates.

Table 5.1: Number of GP practices participating in QFLU in the West Midlands

Number of GP practices participating in QFLU in the West Midlands

5.5 NHS Direct

NHS Direct is a 24 hour nurse-led telephone service that covers England and Wales, established in 1997. It answers half a million calls per month ⁽⁹⁾. It has evolved to provide e-health information via the internet and a digital interactive TV service. The telephone service utilises algorithms from clinical decision support systems so that symptom based advice can be given to the callers. The information from the telephone call centres flows to the National Operations Centre in West Yorkshire and from there to the West Midlands Regional Surveillance Unit where analysis is undertaken of the syndromic surveillance data. From these data the proportion of calls concerning influenza like illnesses and fever can be analysed by different age groups. Seasonal thresholds have been developed based upon the proportion of all calls relating to influenza like illness and fever (see Figure 5.2).

Figure 5.2: Proportion of NHS Direct calls (expressed as a percentage) for cold/flu and fever (5-14 years)

Proportion of NHS Direct calls (expressed as a percentage) for cold/flu and fever (5-14 years)

5.6 Medical Officers of Schools Association (MOSA)

This association was founded in 1884 in response to, "The need for the general adoption of more definite rules for guarding our great educational establishments from the outbreak and spread of preventable infectious disease".

There are currently approximately 400 members of the MOSA; the majority are General Practitioners who are Medical Officers for Independent Schools including boarding schools. The number of schools participating in the scheme to report influenza like illness to the HPA varies weekly, it is usually between 15-25 schools and no data is collected during school holidays.

5.7 Vaccine Uptake

Seasonal influenza vaccines in the England are offered to all those over 65 years of age or individuals living in care homes. Additionally, individuals of any age with chronic conditions are offered the vaccine: heart, lung and renal diseases, cancer or those with lowered immunity.

Figure 5.3: Influenza vaccine uptake in individuals 65 years and older since 2000

Influenza vaccine uptake in individuals 65 years and older since 2000

5.8 Avian Influenza

Avian influenza was first recognised in Italy in 1878. It often causes no disease in wild birds but can cause high mortality in commercial poultry. When large numbers of birds die as a result of an influenza virus it is termed as, ‘highly pathogenic avian influenza’. Avian influenza is currently, at the time of writing this chapter, a disease of birds ⁽²⁾. There is concern that the virus may mutate or combine with a seasonal influenza virus and become more transmissible to humans and under these conditions a pandemic may occur. This is why poultry workers in the UK are being offered seasonal influenza vaccines ⁽⁴⁾.

The current outbreak of Avian Influenza (H5N1) started in mid-2003 in South East Asia. The World Health Organisation are organising and coordinating the global response to avian influenza. It is estimated that 150 million birds have now died globally as a result of H5N1 infection; this is the most severe outbreak in birds ever to have been recorded ⁽²⁾. Transmission to humans is still rare. There have been 315 human cases of H5N1 influenza and of these 191 individuals have died at the time of writing ⁽¹⁶⁾.

Table 5.2: List of countries reporting human H5N1 cases

List of countries reporting human H5N1 cases

The HPA has developed algorithms for suspected human cases of avian influenza in the UK. A database is being developed and tested to allow surveillance information to be obtained should cases occur in the UK ⁽⁷⁾.

To complement surveillance in humans there is surveillance of birds. Animal Health in England carries out an on-going sampling of wild birds to test for H5N1 influenza in England and Wales. There are three components to this surveillance: sampling of live caught wild birds, sampling of wild birds shoot during normal wildfowling activities and screening of wild birds found dead (15).

5.9 Pandemic Influenza

The influenza virus is antigenically unstable. There are two types of glycoprotein on the surface of influenza A viruses; haemagglutinin and neuraminidase. These surface proteins are often changing slightly, due to the instability, and this is called antigenic drift. When a major change in the surface proteins occurs and a new virus emerges this is called antigenic shift ⁽¹⁾. New viruses have the potential to cause a pandemic, as opposed to minor changes that result in seasonal influenza. The conditions required for a pandemic to occur are that there has to have been the development of a new influenza virus with antigenic shift of the surface proteins of the virus, rapid person to person spread in a population leading to large numbers of the population being ill because they have little immunity to the new virus. Pandemics can occur at any time of year i.e. they are not limited to the winter months. New influenza virus strains are classified according to the year and the place where they were identified, for example, Spanish ‘flu 1918, Asian ‘flu 1957 and Hong Kong ‘flu 1968/69.

Planning work is being undertaken at regional and national levels to address the surveillance needs that will be required during a pandemic building upon the current seasonal surveillance systems. For some information needs new surveillance systems will have to be developed. The Department of Health are coordinating this in conjunction with many other agencies at a national level as part of the Pandemic Preparedness Program ⁽³⁾.

References:

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