The Clinical characteristics of influenza b infection during the 2011-2012 influenza season

Purpose: This retrospective study was performed to identify the clinical characteristics of influenza B infection and compare to influenza A infection. Methods: Medical records of patients diagnosed with influenza using a multiplex PCR test, admitted to Seoul St. Mary's Hospital, during the 2011-2012 influenza season were analyzed. Clinical and laboratory characteristics of influenza B patients were investigated and compared with those of influenza A patients. Results: A total of 145 influenza patients were enrolled during this study period. Among these, 66 and 78 patients were diagnosed with influenza A and B, respectively, and 1 patient was diagnosed with co-existing influenza A and B. Cough (88.2%), rhinorrhea (77.1%) and sputum (60.4%) were the most common symptoms among these influenza patients, and most were diagnosed with upper respiratory infection (31.9%) or lower respiratory infection (49.3%). In comparison to influenza A patients, influenza B patients were older (4.7±4.1 years vs. 3.3±2.5 years, P =0.016), and the number of fever days before hospitalization were longer (3.0 days vs. 2.5 days, P =0.043). While sore throat (10.3% vs. 1.5%, P =0.039) and vomiting (20.5% vs. 6.1%, P =0.012) were more common in influenza B patients than in influenza A patients, other clinical and laboratory characteristics were not significantly different between the two groups. Conclusions: No significant differences in clinical and laboratory perspectives were manifested in influenza A and B infections. Preventive measures should be emphasized over treatment in influenza B due to prolonged fever duration before admission.