我国北方省份流感病毒活动的时间分布特征

Temporal characteristics of influenza in northern provinces, China

目的描述2006—2011年北方省份流感活动强度的时间趋势和季节性分布特征。方法使用2006年5月至2011年4月15个北方省份的病毒学监测数据，根据流感病毒检测阳性率确定每个月的流行强度。分月检测阳性率为峰值月份检测阳性率的≥30％、10％-30％、〈10％分别定为高、中、低强度流行。将连续的高强度流行的月份定为流感流行季节。结果每年12月至次年2月均为高强度流行，每年6—7月均为低流行，每年3—4月、9—11月均出现过中、高强度流行。每年流感流行季节在9—12月开始，2—4月终止，持续时间4—7个月。除2009年甲流大流行，其他年份活动峰值均落在1月。每年主要流行株不同。结论北方省份流感呈单个流行季节，主要分布在12月至次年2月，3—4月、9—11月流感病毒仍比较活跃。建议北方省份人群接种流感疫苗集中在12月份前，以便起到较好的防控流感疫情的效果。

Objective To study the temporal tendency and seasonal characteristics of the influenza activity intensity in northern provinces during 2006-2011. Methods The monthly intensity of influenza activity was estimated based on monthly influenza positive rate that was calculated from laboratory surveillance data in 15 northern provinces. High, medium and low intensity of influenza activity was defined when monthly influenza positive rate was I〉30% , 10% -30% and 〈 10% in the month of influenza activity peak respectively. An influenza season was defined as the continuous months in which the high intensity was identified. Results In each of the eonsecutive 5 years, the low intensity was identified from June to July, the high intensity was identified from December to February of next year. In some years, the high or medium intensity observed from March to April, and from September to November. The influenza season lasted 4-7 month with the onset from September to December and the end from February to April. The peak month was in January in each of the other years except 2009 Influenza A （ HI N1 ） pdm09 pandemic. The predominant circulating influenza strains varied by year. Conclusion A regular winter pattern is identified in the northern provinces. The influenza season occurred mainly from December to February of next year. Active influenza transmission continued from March to April, and from September to November. We recommend that annual vaccination with seasonal influenza vaccines in northern provinces should be carried out before December to improve effectiveness.