 A United Kingdom investigation of risk factors for hospitalisation and poor outcome with pandemic A / H1N1 influenza looked at 631 patients from 55 hospitals admitted with confirmed infection from May through September 2009. 13 % were admitted to a high dependency or intensive care unit and 5 % died; 36 % were aged < 16 years and 5 % were aged ≥ 65 years. Non-white and pregnant patients were over-represented. 45 % of patients had at least one underlying condition, mainly asthma, and 13 % received antiviral drugs before admission. Of 349 with documented chest x-rays on admission, 29 % had evidence of pneumonia, but bacterial co-infection was uncommon. Multivariate analyses showed that physician-recorded obesity on admission and pulmonary conditions other than asthma or chronic obstructive pulmonary disease (COPD) were associated with a severe outcome, as were radiologically confirmed pneumonia and a raised C-reactive protein (CRP) level (≥ 100 mg / l). 59 % of all in-hospital deaths occurred in previously healthy people.
