Investigation of influenza and respiratory viruses in hospitalised patients with influenza-like illness in an emergency room.

Introduction: Influenza-like illness (ILI) surveillance is usually performed using outpatient data, and information on the surveillance of patients hospitalised for ILI, which is critical for the complete assessment of the influenza burden, is lacking.

Methodology: In this prospective active surveillance study, patients with community-acquired ILI hospitalised for at least 24 hours in the Emergency Room (ER) of Gazi University Hospital were identified according to the ICD-10 codes at hospital admission through active surveillance of the 2013-2014 and 2014-2015 influenza seasons. The presence of influenza and other respiratory viruses was analysed in the nasopharyngeal or pharyngeal specimens by real-time polymerase chain reaction.

Results: 351 patients admitted to emergency room with certain ICD-10 codes were assessed, and 111 patients with ILI were included in the study. We detected 15 influenza and 23 other respiratory viruses in 33 of the 111 patients. More than one virus was detected in 5 patients. No virus was detected in a majority of the patients with ILI. The sensitivity of hospital admission/discharge ICD-10 codes used in the study to detect real influenza cases was low. Patients with influenza were admitted to the hospital more frequently with high fever symptoms compared with patients with influenza virus-negative and other respiratory virus-positive (p < 0.05).

Conclusions: This study revealed that non-influenza respiratory viruses were a major contributor to ILI. Patients admitted with fever during the influenza seasons should be evaluated for influenza virus infection, and the use of diagnostic codes in surveillance studies can lead to incorrect results.