2006至2014年北京单中心儿童乙型流感病毒流行的监测

目的 了解北京单中心儿童乙型流感病毒的流行趋势，为流感的防控提供数据支持。方法 2006年9月至2014年5月对首都儿科研究所附属儿童医院门诊和急诊采集流感样病例的咽拭子标本，采用传代狗肾细胞(MDCK细胞)行流感病毒和副流感病毒的分离，并用特异性血清对分离到的流感病毒进行凝集抑制试验鉴定型别。同时接种人喉癌细胞（HEp-2）行呼吸道合胞病毒和腺病毒的分离。分为8个监测年度，以2006年9月至2007年8月（2006至2007年）为1个监测年度，余7个年度类推。对8个监测年度乙型流感病毒的流行特征行描述性分析，并与同期甲型流感病毒的流行特点进行比较。结果 6 150份咽拭子标本检测了流感病毒，分离到乙型流感病毒345株（5.6％），其中166株（48.1%）B/V系毒株和179株（51.9%）B/Y系毒株。①8个监测年度，出现5个乙型流感病毒的流行高峰。除2006至2007年外， 2007至2008、2009至2010、2011至2012和2013至2014年的流行高峰呈隔年流行的特点，月阳性率最高可达46.2%（2008年1月和2012年2月）。2006至2007、2009至2010、2010至2011和2013至2014年，甲型流感病毒阳性率高于乙型流感病毒，且乙型流感流行高峰均出现在甲型流感流行高峰后；2007至2008和2011至2012年，乙型流感病毒阳性率高于甲型流感病毒，且乙型流感病毒流行高峰均出现在甲型流感流行高峰前。②8个监测年度中2006至2007、2007至2008、2010至2011和2011至2012年B/V系和B/Y系乙型流感病毒同时流行，余4个年度为其中之一流行株流行。2009至2010、2011至2012和2013至2014年的流行株与WHO推荐的流感疫苗中的乙型流感病毒型别相匹配。③345例乙型流感病毒阳性患儿中，～12岁以下组中随着患儿年龄增大而乙型流感病毒阳性率增高。结论 2006年9月至2014年5月北京地区儿童乙型流感病毒的流行基本呈现隔年出现高峰的流行趋势。在2个谱系同时流行的4个流行季中，分别以B/V或B/Y系乙型流感病毒为主要流行株。

Surveillance of influenza B virus epidemic in children with influenza-like illness in Beijing from 2006 to 2014

Objective To investigate the prevalence of influenza B virus epidemic in children with influenza-like illness (ILL) in Beijing.Methods Throat swabs were collected from children with ILL who visited the Children′s Hospital affiliated to Capital Institute of Pediatrics from September 2006 to May 2014. All of the clinical specimens were inoculated into MDCK cells to isolate influenza viruses and parainfluenza viruses followed by identifying different types of influenza viruses with reference antiserum by hemagglutination-inhibition assay. HEp-2 cells were used to isolate human respiratory syncytial virus and adenovirus simultaneously.Results Out of 6 150 throat swabs collected, 345 (5.6%) were positive for influenza B virus, of them 166 (48.1%) belonged to B/Victoria-like (B/V) lineage and 179 (51.9%) were part of B/Yamagata-like (B/Y) lineage. Throughout the eight consecutive influenza seasons, 2 lineages of influenza B co-circulating were found out in 5 seasons. Except 2006-2007 season, influenza B virus predominated every other year in the rest of seven seasons (2007-2008, 2009-2010, 2011-2012 and 2013-2014 seasons), with the highest positive rates of 46.2% in Jan. 2008 and Feb. 2012. B/V or B/Y lineage circulated with a trend of B/Y-B/Y-B/V-B/V-B/Y-B/V-B/V-B/Y, however, matching between the lineages of the influenza B strains within vaccines used and circulating lineages was achieved only in 3 influenza seasons (2009-2010, 2011-2012 and 2013-2014). Most of the activity of influenza B occurred in winter and next spring. Only a few influenza B virus strains could be isolated in non-influenza season. The epidemic peak of influenza B appeared after that of influenza A when the positive rate of influenza A was higher than that of influenza B in 2006-2007, 2009-2010 and 2010-2011, while the epidemic peak of influenza B appeared before that of influenza A when the positive rate of influenza B was higher than that of influenza A in 2007-2008 and 2011-2012. The positive rate of influenza B increased with age in children younger than 12 years old. Co-infection of influenza B with other common respiratory viruses was very rare.Conclusion Influenza B viruses predominated in children every 2 years from September 2006 to May 2014 in Beijing. Cocirculation of B/V or B/Y lineages was found in 4 of 8 consecutive seasons which were predominated by one of lineages.