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Volume 504: debated on Thursday 21 January 2010

To ask the Secretary of State for Health how many persons were recorded as having contracted seasonal influenza in each year since 1998; and how many persons were recorded as having contracted swine influenza in the last 12 months. (312496)

Data on the total numbers of cases of seasonal influenza are not collected.

At the start of the swine flu pandemic, all suspected cases were investigated by laboratory testing. As of 1 July 2009 there were 6,929 confirmed cases of swine flu in the United Kingdom.

From July, however, as case numbers rose rapidly, only a small proportion of suspected cases were laboratory confirmed. From that point onwards, estimates of case numbers were made by the Health Protection Agency (HPA), with the aim of providing an indication of the trend in the occurrence of the disease in the population. It was recognised, however, that there was considerable uncertainty in the case number estimates and, in order to allow for this, wide ranges around the estimates were provided.

A total of 845,000 cases of illness due to influenza infection were estimated to have occurred in the population of England during the pandemic in 2009 based on the published, weekly, HPA estimates up to 20 December 2009 (range 415,000 to 1,662,000). This is recognised to underestimate the true number of people infected due to the occurrence of infection in many others who had either very mild illness or infection with no illness at all.