The United Kingdom 2009 Swine Flu Outbreak As Recorded in Real Time by General Practitioners

Background. Initially the course of the 2009 swine flu pandemic was uncertain and impossible to predict with any confidence. An effective prospective data resource exists in the United Kingdom (UK) that could have been utilized to describe the scope and extent of the swine flu outbreak as it unfolded. We describe the 2009 swine flu outbreak in the UK as recorded daily by general practitioners and the potential use of this database for real-time tracking of flu outbreaks. Methods. Using the General Practice Research Database, a real-time general practice, electronic database, we estimated influenza incidence from July 1998 to September 2009 according to age, region, and calendar time. Results. From 1998 to2008, influenza outbreaks regularly occurred yearly from October to March, but did not typically occur from April to September until the swine flu outbreak began in April 2009. The weekly incidence rose gradually, peaking at the end of July, and the outbreak had largely dissipated by early September. Conclusions. The UK swine flu outbreak, recorded in real time by a large group of general practitioners, was mild and limited in time. Simultaneous online access seemed feasible and could have provided additional clinical-based evidence at an early planning stage of the outbreak. 1. Introduction An outbreak of influenza in Mexico in April 2009 was found to be due to a new H1N1 strain of influenza A (subsequently referred to as “swine flu”). A worldwide spread of the virus rapidly ensued. Initially, the nature and scope of a swine flu pandemic was uncertain and, in view of the high variability of influenza outbreaks in the past 40 years, it was impossible to predict with any confidence [1–5]. In the UK and elsewhere, influenza surveillance systems have operated for decades to follow the course of such outbreaks, and subsequent to the initial swine flu outbreak additional surveillance efforts were instituted in the UK (http://www.hpa.org.uk/). In the June 20, 2009 issue of The Lancet, Tran and colleagues commended the UK efforts to address the outbreak, but noted that “our major concern about the current response to H1N1 has been the dearth of any systematic, prospective, patient-oriented clinical research alongside the commendable public health response to the pandemic” [6]. In fact, an effective, systematic, prospectively designed data resource did exist in the UK at the time and could have been used to describe the course of the outbreak in the general population, as diagnosed by a representative sample of some 1000 general practitioners on a daily basis,