Clinical study of the time course of clinical symptoms of Pandemic (H1N1) 2009 influenza observed in young adults during an initial epidemic in Kobe, Japan.

Objective: Although the rates of reported symptoms of Pandemic (H1N1) 2009 influenza virus infection are well studied, the course of progression of these symptoms is not clear. In this study, we carefully reviewed the progress of each patient after hospitalization and clarified the clinical course of the symptoms.

Methods: We retrospectively examined the clinical data of 16 consecutive patients who had been hospitalized during the early stages of an influenza epidemic and observed the clinical progression of their symptoms.

Results: Each symptom had a different time of onset and progression pattern. In roughly one-third of our patients, symptoms appeared before the onset of high fever. Acute respiratory symptoms tended to last longer than other symptoms; similarly, sore throat and cough lasted longer than rhinorrhea. The SpO(2) of the patients with influenza showed a declining trend. The point at which minimum SpO(2) levels were noted was approximately 1.5 days after onset of fever.

Conclusion: In this H1N1 epidemic, patients typically tended to experience general fatigue, sore throat, and cough before the onset of fever, with sore throat and cough lasting longer than the other symptoms. Most patients showed decreased SpO(2) levels at -1.5 days after onset of fever.