A pandemic response to a disease of predominantly seasonal intensity.

From the recognition of the swine flu pandemic in late April 2009, health professionals, politicians and the public needed to know how serious pandemic (H1N1) 2009 influenza (swine flu) was in relation to other seasonal strains of influenza. The Victorian experience suggests that the circulation of pandemic (H1N1) 2009 influenza in the community was at most like influenza circulation in a season of moderate seasonal activity. We have no estimate of the total case count, but we know most infections have been mild. However, while disease in the community appears mild, and the risk of hospitalisation is low, a high proportion of patients hospitalised with swine flu required intensive care. Deaths from swine flu have not been as numerous as the modelled deaths from seasonal influenza, although people dying from swine flu are younger. Because we do not understand the laboratory-confirmed burden of disease due to seasonal influenza (as opposed to the modelled burden of disease), we could not base our response to the pandemic on an informed comparison of seasonal and pandemic influenza. We may not have needed a pandemic response to a disease that, although it has a different footprint, has been predominantly of seasonal intensity. It is critical to accumulate quality evidence about laboratory-confirmed influenza to guide our intervention policies for both seasonal and pandemic influenza.