Pandemic (H1N1) 2009 in England: an overview of initial epidemiological findings and implications for the second wave

Contents Executive summary 2 Pandemic (H1N1) 2009 in England: an overview of initial epidemiological findings and implications for the second wave 4 References 20 Annexe: Methods and data sources 22 1 Pandemic (H1N1) 2009 in England: an overview of initial epidemiological findings and implications for the second wave Executive summary The Health Protection Agency (HPA), working with key partners including the Devolved Administrations, the Department of Health and the National Health Service (NHS), has undertaken a vigorous response to pandemic (H1N1) 2009. This report describes the HPA's response to the first wave of pandemic (H1N1) 2009 in England from April to the end of September 2009, summarises key findings about the pandemic and assesses the implications of this information for the second wave. The initial response in England centered on a containment strategy: individual cases were investigated and treated with antivirals and their contacts were traced and offered antiviral prophylaxis. In addition, schools were typically closed if confirmed case(s) were identified and close contacts offered prophylaxis. In mid-May, Flu Response Centres were established in each of the 10 Strategic Health Authority regions of England to support these intensive efforts initially undertaken by the HPA's 26 Health Protection Units. Nonetheless, case numbers continued to rise and the occurrence of large outbreaks in parts of the country indicated the spread of the pandemic virus. On 2 July a 'treatment-only' phase was initiated to manage the pandemic: oseltamivir was offered to anyone who had an appropriate clinical illness, without the need for testing. Shortly thereafter the telephone-and internet-based National Pandemic Flu Service (NPFS) was launched to authorise access to antivirals. During the first wave of pandemic (H1N1) 2009 in England it is estimated that between 144,000 and 670,000 people (mid-estimate of 320,000) fell ill. However, this varied considerably by age group and region. People aged 24 years and younger were many more times likely to become infected than adults >65 years. Using modelled estimates, London and the West Midlands accounted for 30% and 12%, respectively, of clinical cases in England to the end of September. Most people experienced a mild, typical influenza-like illness and the number of deaths in the first wave has been far fewer, compared with a typical influenza season. However, severe cases have occurred and the overall rate of hospitalisation ranged from 1.3% to 2.5%. The likelihood of hospitalisation increased in the presence of one or more risk conditions, particularly …