Influenza A(H1N1)pdm09 in England, 2009 to 2011: a greater burden of severe illness in the year after the pandemic than in the pandemic year.

Influenza pandemics are often perceived as single-year events, but the burden of previous influenza pandemics has in reality been spread over a number of years. The aim of this paper is to compare the burden of influenza in the pandemic year 2009/10 with that in the year immediately after (2010/11) in England. We compared four measures of disease. There was a greater burden of severe illness in 2010/11 compared with 2009/10: more deaths (474 vs 361), more critical care admissions (2,200 vs 1,700), and more hospital admissions (8,797 vs 7,879). In contrast, there were fewer general practice consultations in 2010/11 compared with 2009/10 (370,000 vs 580,000). There was also much less public interest in influenza, as assessed by number of Google searches. This is a worrying finding, as by the time of the second influenza season, much had been learnt about the potential impact of the influenza A(H1N1)pdm09 virus and an effective vaccine developed. We suggest that a widespread assumption of 'mildness' led to insufficient ongoing action to prevent influenza and hence to avoidable influenza-related deaths. This offers a lesson to all countries, both for future influenza seasons and for pandemic preparedness planning.