Ching-Fen Shen¹, Shu-Ching Huang¹, Shih-Min Wang², Jen-Ren Wang³, Ching-Chuan Liu¹
Departments of ¹Pediatrics and ²Emergency Medicine, National Cheng Kung University Medical College and Hospital, and ³Department of Medical Laboratory Science and Biotechnology, National Cheng Kung University, Tainan, Taiwan

Received: May 12, 2007     Revised: June 11, 2007     Accepted: June 30, 2007

Corresponding author: Dr. Ching-Chuan Liu, Department of Pediatrics, College of Medicine, National Cheng Kung University MedicalCollege and Hospital, 138, Sheng Li Road, Tainan 70428, Taiwan. E-mail: This e-mail address is being protected from spam bots, you need JavaScript enabled to view it

Background and Purpose: An outbreak of influenza A and influenza B appeared at the beginning and end of 2006 in southern Taiwan. We conducted this study to test whether laboratory findings could differentiate influenza A from influenza B infection.

Methods: All children aged 16 years or less, who had nasal and/or throat swabs sent from inpatient or out-patient settings at National Cheng Kung University Hospital for the diagnosis of influenza infection from January 2005 to February 2007, were considered eligible subjects. Retrospective chart review of clinical and laboratory data was performed.

Results: 274 patients were enrolled, 151 with influenza A and 123 with influenza B, of whom 127 (46.4%) received laboratory examinations. The peak month of influenza A and influenza B infections was January 2006 and January 2007, respectively. Children with influenza B infections were older than those with influenza A infections (p<0.001). Influenza B-infected patients were more likely to have myalgia (p=0.004) than those with influenza Ainfections. Furthermore, children with influenza B infections tended to have lower leukocyte counts (6383 ± 3970/mm³ vs 7639 ± 3476/mm³, p=0.004), and higher serum creatine kinase level (p=0.002) than those withinfluenza A infections. The clinical outcomes were usually favorable.

Conclusions: The clinical features of influenza B and influenza A infections are similar. However, decreased leukocytes and increased serum creatine kinase can be used as adjunctive criteria for diagnosis of influenza B infection before viral culture results are available.

Key words: Child; Differential diagnosis; Influenza A virus; Influenza B virus; Leukopenia

J Microbiol Immunol Infect. 2008;41:294-300.