目的：探讨流感病毒B的流行特征和儿童单纯B型流感病毒（influenza virus B,IVB）肺炎的临床特征。方法：分析苏州大学附属儿童医院2008年冬季至2011年冬季因呼吸道感染住院治疗并进行病原学检查的患儿临床资料。结果：（1）2008、2009、2010年冬季流感病毒(A+B)检出率分别为0.89%、5.49%和6.24%，2011年冬季患儿流感病毒(A+B)检出率为8.72%,显著高于前3年。2008、2009、2010、2011年冬季IVB检出率分别为0%、0%、0.21%和5.36%，2011年冬季IVB检出率显著高于前3年。（2）2011年检出IVB肺炎患儿94例，其中单纯IVB肺炎27例。（3）单纯IVB肺炎患儿发病年龄以6个月以上为主；临床表现以发热（85%）、流涕（89%）、咳嗽（100%）为主，部分伴喘息（26%），少见呼吸困难（7%）；少数白细胞异常（19%），部分CRP增高（30%），前白蛋白大多降低（70%），未见明显脏器功能损害；影像学表现无特异性；大部分患儿多个体液细胞免疫指标异常；平均住院时间1周左右，无重症病例，预后好。结论：2011年冬季住院患儿流感活动呈高峰；IVB活动逐渐增强。单纯IVB肺炎重症病例少，临床症状无特异性，预后较好。

OBJECTIVE: To investigate the epidemiological features of influenza virus B (IVB) in the winter and the clinical features of pediatric pneumonia caused by IVB only. METHODS: A retrospective study was performed on the clinical data of children with respiratory infection who received pathogen testing and therapy at Soochow University Affiliated Children′s Hospital during the winters of 2008, 2009, 2010 and 2011. RESULTS: The positive rates of influenza viruses A and B in the winters of 2008, 2009, and 2010 were 0.89%, 5.49%, and 6.24% respectively; the positive rate of influenza viruses A and B in the winter of 2011 was 8.72%, significantly higher than those in 2008-2010. The positive rates of IVB in the winters of 2008, 2009, and 2010 were 0%, 0%, and 0.21% respectively; the positive rate of IVB in the winter of 2011 was 5.36%, which was significantly higher than in the years 2008 to 2010. Pneumonia caused by IVB was confirmed in 94 children during the winter of 2011, including 27 cases of pneumonia caused by IVB only. Most of children with pneumonia caused by IVB only were aged over 6 months. The common symptoms in the 27 children caused by IVB only were fever (85%), runny nose (89%), and cough (100%). Wheezing (26%) and dyspnea (7%) were also seen in some cases. Among the 27 children, 19% showed abnormal white blood cell count, 30% showed increased C-reactive protein, 70% showed decreased prealbumin, and none showed visible organ dysfunction. No specific imaging findings were seen in the children with pneumonia caused by IVB only. Howerer, many abnormal humoral and cellular immunological parameters were found in the majority of these children. The average length of hospital stay was approximately one week, there were no critical patients and the prognosis was good. CONCLUSIONS: Influenza viruses were at a peak level in inpatient children in the winter of 2011. IVB infection rate was gradually increasing. In children with pneumonia caused by IVB only, there are few critical patients, the symptoms are nonspecific and the prognosis is good.