The following provides background information on the purpose of influenza surveillance and the changes to the influenza surveillance systems over time and, in particular, following the 2009 influenza pandemic. It also contains information on influenza activity for previous seasons.
The key purpose of influenza surveillance is to inform the planning, implementation and evaluation of public health intervention programmes and disease control. Influenza surveillance is integral to the effective planning, implementation and monitoring of the annual influenza immunisation programme. Since 1972 rates of influenza-like illness (flu) seen by general practitioners has been monitored weekly across Scotland (see SERVIS and flu spotter sections below). The way in which this flu data has been captured has changed over the years; however, the common method of presentation has remained constant. This has been to express GP consultations as a rate per hundred thousand of the population. Typically an all-Scotland consultation rate is presented. During the 2009 pandemic, a pre-planned surveillance development PIPeR was expanded to provide a comprehensive surveillance information to meet the needs of the pandemic. This led to the development of SISRS which is currently the mainstay for GP influenza-like illness in Scotland.
In light of the spectrum of influenza illness a range of surveillance systems have been developed in addition to GP surveillance systems to meet the needs of seasonal and pandemic influenza. These are described in our weekly report. There is no single flu surveillance component that can describe the onset, severity and impact of influenza or the success of its control measures each season across a community. To do so requires a number of complimentary surveillance components which are either specific to influenza or its control e.g. NHS24 cold/flu calls, severe influenza monitoring or influenza vaccine uptake and antiviral prescribing patterns. Information on excess all-cause deaths is also monitored. The influenza surveillance systems developed in Scotland are very similar to other parts of the UK. Please refer to the Annual PHE Respiratory Virus report.
Scottish Influenza Surveillance Reporting Scheme (SISRS)
The Scottish Influenza Surveillance Reporting Scheme (SISRS) was devised to provide more comprehensive surveillance during the pandemic of influenza. It included aggregated data from almost all GP practices in Scotland thus improving the geographical coverage of surveillance of GP consultations. It gave a more complete picture of changes within individual NHS boards and provided a signal to them if consultations were increasing within their areas. The system was designed to add to the information already in existence through the PIPeR system.
Since the 2010/11 season the main source of this data for general practice has been the Scottish Influenza Surveillance Reporting Scheme (SISRS). This scheme began in August 2009, providing daily consultation rates for influenza-like illness (ILI) and acute respiratory illness (ARI), by practice, age and sex. Around 950 practices (99% of all practices in Scotland) routinely report into this scheme. ILI rates, rather than ARI rates are reported every week to make Scottish data more comparable to data from the rest of the UK and beyond. Each season a threshold or baseline value is needed to determine when flu is circulating in the community and when a country has entered into ’normal‘ seasonal activity. For more information on how this is calculated please refer to the technical document.
Pandemic Influenza Primary Care Reporting (PIPeR)
Data output from the pre-existing primary care surveillance system of influenza-like illness in Scotland (Pan Influenza Primary care Reporting or PIPeR) provided daily clinical presentation with influenza-like illness (ILI) or acute respiratory infections (ARI) in season in real time. The data in the 2009/10 season was restricted to 37 (mainly PTI) practices across Scotland. The PIPeR system routinely extracted and transmitted data already held in General Practice clinical information systems on influenza (and pneumococcal) vaccine use and clinical presentation with ILI or ARI, as recorded using Read codes. Such data allows trend data on clinical presentation (spanning the period 2003 to 2010) and timely clinical effectiveness data on seasonal (and in 2009/10 pandemic) influenza vaccine effectiveness.
Historical Influenza Surveillance Systems
Scottish Enhanced Respiratory Virus Infection Surveillance (SERVIS)
Winter 2000/2001 saw the introduction of SERVIS (Scottish Enhanced Respiratory Virus Infection Surveillance). SERVIS was an integrated approach to influenza surveillance which offers a more detailed and accurate picture of the influenza outbreak during the winter season. The main component of SERVIS was the provision of age specific clinical data from sentinel PTI (practice team information) general practices with linked virological testing in a small sample of consultations from each practice. There were 59 sentinel computerised PTI practices in Scotland covering 13 NHS board areas. PTI practices provided not only weekly-recorded data of influenza like illness (ILI) cases by age and sex, but also consultations for acute respiratory infection (ARI). In conjunction with clinical PTI data, combined nasal and throat swabs were obtained from patients displaying flu-like symptoms for multiplex PCR testing at Glasgow's Regional Virus Laboratory. PCR testing provided real time data (results in 48hrs) identifying influenza and other circulating respiratory viruses. Overall therefore, SERVIS was well placed to provide ongoing surveillance of influenza and other respiratory viruses in circulation with timely information on numbers of consultations and circulating virus types, as well as age groups affected and regional breakdowns.
Flu Spotter scheme
The Scottish flu spotter scheme collated reports of flu-like illness during the winter flu season in Scotland for 37 years. By the end of this period the scheme provided estimated consultations for flu-like illness from 90 practices in 13 NHS board areas covering around 78% of the Scottish population. The scheme, together with SERVIS, was part of a group of early warning systems operating throughout Europe which contribute data from clinical consultations and laboratory tests to the European Influenza Surveillance Scheme (EISS) – the precursor of the flu reporting now collated by the European Centre for Disease Prevention and Control (ECDC). The European scheme seeks collected data over a minimum period of week 40 and week 20 of the following year (roughly October to May). This allowed for the surveillance of unusually early or late outbreaks, and the measurement of background levels of activity allows direct comparisons to be made between countries. The benefits of the scheme included facilitation of healthcare and disease control planning, as well as furthering our understanding of the epidemiology of influenza, which is of particular interest with the ever-present threat of an international flu pandemic arising in the future.
Previous Influenza Seasons