Clinical differences between influenza A (H1N1) virus and respiratory infection between the two waves in 2009 and 2010

Paul Zarogoulidis,^1,2 Dimitrios Glaros,¹ Ioannis Kioumis,² Eirini Terzi,¹ Konstantinos Porpodis,² Anastasios Tsiotsios,² Anastasios Kallianos,³ Georgia Trakada,⁴ Nikolaos Machairiotis,¹ Aikaterini Stylianakil,¹ Antonis Sakas,¹ Ageliki Rapti,³ Nikolaos Courcoutsakis,⁵ Theodoros C Constantinidis,⁶ Efstartios Maltezos,¹ Konstantinos Zarogoulidis<sup>2

1</sup>Unit of Infectious Diseases, General University Hospital of Alexandroupolis, Democritus University of Thrace, Komotini, ²Pulmonary Department, "G Papanikolaou" General Hospital, Aristotle University of Thessaloniki, Thessaloniki, ³Second Pulmonology Clinic, Hospital of Chest Diseases "Sotiria", Athens, ⁴Pulmonary Department, "Alexandra" General Hospital, University of Athens, Athens, ⁵Radiology Department, University General Hospital of Alexandroupolis, ⁶Laboratory of Hygiene and Environmental Protection, Occupational Medicine Section, Democritus University of Thrace, Komotini, Greece

Background: The purpose of the present retrospective study was to examine the clinical differences between patients hospitalized with H1N1 virus and those hospitalized with nonvirus respiratory tract infection in 2009 and 2010.
Methods: Adult patient data were collected from three tertiary hospital centers. Real-time reverse transcriptase polymerase chain reaction testing was used to confirm the diagnosis. We included 106 H1N1-positive patients (52 from 2009 and 54 from 2010). These data were compared with those from 108 patients with H1N1-negative respiratory tract infection (51 patients from 2009 and 57 from 2010).
Results: In 2009, the mean age was 36.4 years for H1N1-positive patients versus 46.4 years for H1N1-negative patients, and mean body mass index (BMI) was 26.4 kg/m² patients and 28.1 kg/m², respectively. In 2009, seven patients required intubation, six of whom were H1N1-positive. In 2010, the mean age was 43.8 years for H1N1-positive patients versus 60.2 years for H1N1-negative patients, and mean BMI was 32.3 kg/m² and 26.9 kg/m², respectively. In 2010, six patients required intubation, three of whom were H1N1-positive. Abnormal chest x-ray findings were found significantly more frequently in H1N1-negative patients than in H1N1-positive patients.
Conclusion: In comparison with 2009, H1N1-positive patients in 2010 were older, were more likely to be obese, and had more severe clinical and laboratory perturbations. However, this did not affect their outcomes. H1N1-negative patients were older in comparison with those who were H1N1-positive, and had more severe clinical and laboratory perturbations.

Keywords: clinical characteristics, influenza A, H1N1, respiratory infection