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Clinical characteristics of adult patients with influenza B and A infections during 2013/2014 flu season

Session: Poster Abstract Session: Viral Infections: Epidemiology
Friday, October 10, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
Background: Human infection caused by influenza B virus (IFV-B) has been known to be less severe than that caused by influenza A virus (IFV-A). Although more recent studies did not find any significant differences between the clinical features of patients with IFV-B and those with IFV-A, clinical data are still lacking on this subject, especially in adult patients.

Methods: This study was performed in Chung-Ang University Hospital, Seoul, South Korea. An adult (>15 years of age) patient, who received a rapid influenza antigen detection test or a respiratory virus multiplex reverse transcriptase PCR test between January and March 2014 and was influenza-positive, was included in this study.

Results: In comparisons for 137 admitted patients (A in 90 and B in 37), baseline characteristics of the IFV-B group did not differ from those of the IFV-A group. Initial clinical symptoms were similar between the two groups, except more frequent sputum production in the IFV-B group (82.6% vs. 61.1%, P = 0.01). Development of pneumonia was not different between the two groups (15.6% in IFV-A vs. 21.3% in IFV-B, P = 0.40). Oxygen therapy, antiviral therapy, and mechanical ventilation was similarly performed between the two groups, whereas vasoconstrictors were more commonly used in the IFV-B group (6.4% vs. none, P = 0.04). Intensive care unit admission was more common in the IFV-B group (10.6% vs. 2.2%, P = 0.047), whereas in-hospital mortality (none in IFV-A vs. 2.3% in IFV-B, P = 0.34) and the mean days of hospital admission (11.3 days vs. 9.7 days, P = 0.56) were not different between the two groups. In comparisons for patients of outpatient deparment (OPD) (A in 121 and B in 105), mean age was higher (41.6 yr vs. 35.3 yr, P = 0.001), and sputum production (72.4% vs. 41.3%, P <0.001) and sore throat (82.9% vs. 70.2%, P = 0.03) were more common in the IFV-B group, whereas the median number of hospital visit were not different between the two groups (1 vs. 1, P= 0.44).

 Conclusion: In adult patients with influenza infection, a few clinical features were more prominent in IFV-B than IFV-A both for admitted and OPD patients, whereas clinical outcomes were not different. IFV-B infection was not milder than IFV-A.

Mi Young Ahn, Seong-Ho Choi, M. D. and Jin-Won Chung, Division of Infectious Diseases, Department of Internal Medicine, Chung-Ang University Hospital, Seoul, South Korea


M. Y. Ahn, None

S. H. Choi, None

J. W. Chung, None

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