Clinical features of influenza virus infection of 2013/2014 season

Introduction: Influenza is an infectious viral disease, with symptoms ranging from mild to severe. Generally the prognosis is good, with many patients spontaneously recovering. However, understanding the clinical characteristics of severe disease is important. Methods: Sixty adults diagnosed with influenza infection in our hospital from October 2013 to April 2014 were included in this study. Diagnoses were confirmed by rapid antigen testing or PCR of respiratory tract specimens. Severe disease was characterized by hospitalization. Comparisons were made between severe and non-severe cases, and among severe cases, depending on the need for mechanical ventilation. Results: Of the patients studied, 23 were severe and 37 were non-severe. All patients classified as severe were administered an oral or intravenous anti-influenza drug. The mean length of hospitalization was 10.1 days (range: 3–24 days) in vaccinated patients, 24.4 days (range: 4–126 days) in unvaccinated patients. Older people and those with a medical history of diabetes were more frequently observed among severe cases than non-severe cases. Among the severe cases, unvaccinated patients and those with a medical history of diabetes more often required mechanical ventilation. Patients infected by influenza A virus and those experiencing symptoms other than upper respiratory tract symptoms were more frequent among severe cases, especially among those needing mechanical ventilation. Conclusion: Age, diabetes, the lack of vaccination, influenza A and the lack of upper respiratory tract symptoms were all factors more frequently observed in severe cases of infection and may contribute to the progression from mild to severe disease.