Asthmatics hospitalised because of influenza A infection are less likely to require
intensive care or die compared with nonasthmatics. The reasons for this are unknown.
We performed a retrospective analysis of data on 1520 patients admitted to 75 UK hospitals with
confirmed influenza A/H1N1 2009 infection. A multivariable model was used to investigate reasons
for the association between asthma and severe outcomes (intensive care unit support or death).