Department of Microbiology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, 610041, China.
Sichuan Center for Disease Control and Prevention, No. 6 Zhongxue Road, Wuhou District, Chengdu, 610041, Sichuan, People's Republic of China.
BMC Infect Dis. 2019 Jan 25;19(1):89. doi: 10.1186/s12879-019-3689-9.
Seasonal patterns of influenza A subtypes and B lineages in tropical/subtropical regions across age have remained to be explored. The impact of the 2009 H1N1 pandemic on seasonal influenza activity have not been well understood.
Based on a national sentinel hospital-based influenza surveillance system, the epidemiology of influenza virus during 2006/07-2015/16 was characterized in the subtropical city, Chengdu. Chengdu is one of the most populous cities in southwestern China, where the first reported case of A/H1N1pdm09 in mainland China was identified. Wavelet analysis was applied to identify the periodicities of A/H3N2, seasonal A/H1N1, A/H1N1pdm09, Victoria, and Yamagata across age, respectively. The persistence and age distribution patterns were described during the pre-pandemic (2006/07-2008/09), pandemic (2009/10), and post-pandemic (2010/11-2015/16) seasons.
A total of 10,981 respiratory specimens were collected, of which 2516 influenza cases were identified. Periodicity transition from semi-annual cycles to an annual cycle was observed for composite influenza virus as well as A/H3N2 along in Chengdu since the 2009 H1N1 pandemic. Semi-annual cycles of composite influenza virus and A/H3N2 along were observed again during 2014/15-2015/16, coinciding with the emergence and predominance of A/H3N2 significant antigenic drift groups. However, A/H1N1pdm09, Victoria, and Yamagata generally demonstrated an annual winter-spring peak in non-pandemic seasons. Along with periodicity transitions, age groups with higher positive rates shifted from school-aged children and adults to adults and the elderly for A/H1N1pdm09 during 2009/10-2010/11 and for A/H3N2 during 2014/15-2015/16.
Differences in periodicity and age distribution by subtype/lineage and by season highlight the importance of increasing year-round influenza surveillance and developing subtype/lineage- and age-specific prevention and control measures. Changes of periodicity and age shifts should be considered in public health response to influenza pandemics and epidemics. In addition, it is suggested to use quadrivalent influenza vaccines to provide protection against both influenza B lineages.
在热带/亚热带地区，各年龄段的甲型流感亚型和 B 系的季节性模式仍有待探索。2009 年 H1N1 大流行对季节性流感活动的影响尚未得到充分了解。
基于国家哨点医院流感监测系统，对亚热带城市成都 2006/07-2015/16 年期间流感病毒的流行病学特征进行了描述。成都作为中国西南部人口最多的城市之一，中国首例 A/H1N1pdm09 病例就在此地发现。分别对 A/H3N2、季节性 A/H1N1、A/H1N1pdm09、维多利亚和 Yamagata 进行了小波分析，以确定其在各年龄段的周期性。描述了大流行前（2006/07-2008/09 年）、大流行期间（2009/10 年）和大流行后（2010/11-2015/16 年）各季节的持续性和年龄分布模式。
共采集呼吸道标本 10981 份，检出流感病例 2516 例。自 2009 年 H1N1 大流行以来，成都复合流感病毒和 A/H3N2 的季节性周期从半年度周期转变为年度周期。2014/15-2015/16 年期间，复合流感病毒和 A/H3N2 再次出现半年度周期，这与 A/H3N2 显著抗原漂移群体的出现和流行相一致。然而，A/H1N1pdm09、维多利亚和 Yamagata 在非流行季节通常表现为冬春季高峰。随着周期性的转变，2009/10-2010/11 年期间 A/H1N1pdm09 和 2014/15-2015/16 年期间 A/H3N2 的阳性率较高的年龄组从学龄儿童和成年人转变为成年人和老年人。
不同亚型/谱系和季节的周期性和年龄分布差异突出了加强全年流感监测和制定针对亚型/谱系和年龄的预防和控制措施的重要性。流感大流行和流行期间应考虑周期性变化和年龄变化。此外，建议使用四价流感疫苗为两种乙型流感提供保护。
