Research Base of Key Laboratory of Surveillance and Early Warning of Infectious Disease, Pudong New Area Center for Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Shanghai, China; School of Public Health and Social Work, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
Research Base of Key Laboratory of Surveillance and Early Warning of Infectious Disease, Pudong New Area Center for Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Shanghai, China.
Int J Infect Dis. 2019 Apr;81:57-65. doi: 10.1016/j.ijid.2019.01.027. Epub 2019 Jan 23.
Understanding the complexity of influenza subtype seasonality is critical to promoting a suitable vaccination program. The aim of this study was to identify and compare the seasonality and epidemiological features of seasonal influenza subtypes after the 2009 A/H1N1 pandemic and to lay a foundation for further investigation into the social and environmental factors affecting seasonal influenza virus transmission.
Influenza-like illness (ILI) case surveillance was conducted in two sentinel hospitals in Pudong New Area, Shanghai between 2012 and 2018. Weekly data on ILI cases were analyzed. A time-series seasonal decomposition analysis was used to reveal the seasonality of influenza and epidemiological features among different subtypes.
In total, 10977 ILI patients were enrolled of whom 2385 (21.7%) had laboratory-confirmed influenza. Compared to influenza A (16.3%), influenza B (5.4%) was less frequently detected among the ILI patients (p<0.001). Semiannual epidemic peaks were identified in four of the years during the 6-year study period, while only one annual epidemic peak was found in the other two years. An epidemic peak occurred in each winter season, and a secondary peak also occasionally occurred in summer or spring. A/H3N2 predominated in both summer and winter, while A/H1N1, B/Yamagata, and B/Victoria circulated almost exclusively in winter or spring. Two lineages of influenza B seemed to predominate in alternating years.
This study highlights the complexity of seasonal influenza virus activity in a subtropical region of China, presenting both semiannual and annual epidemic peaks in different years. The results of this study may provide further insight into possible improvements in the timing of influenza vaccination in Shanghai, China.
了解流感亚型季节性的复杂性对于促进合适的疫苗接种计划至关重要。本研究旨在确定和比较 2009 年甲型 H1N1 大流行后季节性流感亚型的季节性和流行病学特征，并为进一步研究影响季节性流感病毒传播的社会和环境因素奠定基础。
2012 年至 2018 年，在上海市浦东新区的两家哨点医院开展流感样病例（ILI）监测。每周分析 ILI 病例数据。采用时间序列季节性分解分析揭示流感和不同亚型的流行病学特征。
共纳入 10977 例 ILI 患者，其中 2385 例（21.7%）经实验室确诊为流感。与甲型流感（16.3%）相比，乙型流感（5.4%）在 ILI 患者中较少被检测到（p<0.001）。在 6 年的研究期间，有 4 年出现了半年流行高峰，而另外 2 年只出现了一个年度流行高峰。每年冬季都会出现流行高峰，夏季或春季也偶尔会出现次高峰。A/H3N2 在夏季和冬季均占优势，而 A/H1N1、B/Yamagata 和 B/Victoria 几乎仅在冬季或春季流行。乙型流感有两种谱系，似乎在交替的年份占优势。
本研究强调了中国亚热带地区季节性流感病毒活动的复杂性，不同年份既有半年流行高峰，也有年度流行高峰。本研究结果可能为进一步改进中国上海流感疫苗接种时间提供更多的认识。
