Comparison of adult patients hospitalised with pandemic (H1N1) 2009 influenza and seasonal influenza during the "PROTECT" phase of the pandemic response

Letter to the Editor addressing Chang and colleagues due to concern that these assertions underemphasise the true severity of the influenza pandemic, and have led to inappropriate reporting in the media. It is also likely that some of the five untypeable patients who were categorised in the seasonal influenza group had had false-negative test results for pandemic (H1N1) 2009 influenza. Despite the small numbers, this study suggested that patients with pandemic (H1N1) 2009 influenza were younger and less immunocompromised than those with seasonal influenza; both of these characteristics of the patients affected may indicate that the pandemic virus is a more virulent strain. The significant concern is that our community will underestimate the real burden of the pandemic, which was substantial in Australia and New Zealand during the recent winter.