Identifying features that differentiate patients with H1N1 influenza infection from those with other conditions may assist clinical decision making during waves of pandemic influenza activity.
From April 27 to June 15, 2009, nasopharyngeal swabs were obtained from all adults presenting to two urban emergency departments (EDs) with illness including fever or respiratory symptoms. H1N1 infection was detected by reverse transcriptase-polymerase chain reaction. Chart review was performed to compare cases of H1N1 influenza (n ?=? 117) to matched controls.
The median age of cases was 35 years versus 50 years for controls (p