Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
Institute of Epidemiology, Disease Control and Research, Dhaka, Bangladesh.
Lancet Glob Health. 2022 Aug;10(8):e1150-e1158. doi: 10.1016/S2214-109X(22)00212-1. Epub 2022 Jun 13.
Seasonal and avian influenza viruses circulate among human and poultry populations in Bangladesh. However, the epidemiology of influenza is not well defined in this setting. We aimed to characterise influenza seasonality, examine regional heterogeneity in transmission, and evaluate coseasonality between circulating influenza viruses in Bangladesh.
In this retrospective, time-series study, we used data collected between January, 2010, and December, 2019, from 32 hospital-based influenza surveillance sites across Bangladesh. We estimated influenza peak timing and intensity in ten regions using negative binomial harmonic regression models, and applied meta-analytic methods to determine whether seasonality differed across regions. Using live bird market surveillance data in Dhaka, Bangladesh, we estimated avian influenza seasonality and examined coseasonality between human and avian influenza viruses.
Over the 10-year study period, we included 8790 human influenza cases and identified a distinct influenza season, with an annual peak in June to July each year (peak calendar week 27·6, 95% CI 26·7-28·6). Epidemic timing varied by region (I=93·9%; p<0·0001), with metropolitan regions peaking earlier and epidemic spread following a spatial diffusion pattern based on geographical proximity. Comparatively, avian influenza displayed weak seasonality, with moderate year-round transmission and a small peak in April (peak calendar week 14·9, 95% CI 13·2-17·0), which was out of phase with influenza peaks in humans.
In Bangladesh, influenza prevention and control activities could be timed with annual seasonality, and regional heterogeneity should be considered in health resource planning. Year-round avian influenza transmission poses a risk for viral spillover, and targeted efforts will be crucial for mitigating potential reassortment and future pandemic threats.
Canadian Institute of Health Research Vanier Canada Graduate Scholarship.
季节性流感病毒和禽流感病毒在孟加拉国的人类和家禽群体中传播。然而，在这种环境下，流感的流行病学情况尚未得到充分明确。我们旨在描述流感的季节性，检验传播过程中的区域异质性，并评估孟加拉国流行的流感病毒之间的同期性。
在这项回顾性时间序列研究中，我们使用了 2010 年 1 月至 2019 年 12 月期间在孟加拉国 32 个基于医院的流感监测点收集的数据。我们使用负二项式谐波回归模型来估计十个地区的流感高峰时间和强度，并应用荟萃分析方法来确定地区间的季节性是否存在差异。我们利用孟加拉国达卡的活禽市场监测数据来估计禽流感的季节性，并检验人类流感病毒和禽流感病毒之间的同期性。
在 10 年的研究期间，我们纳入了 8790 例人类流感病例，并确定了一个明显的流感季节，每年的高峰出现在 6 月至 7 月（高峰日历周 27.6，95%CI 26.7-28.6）。流行时间因地区而异（I=93.9%；p<0.0001），大都市地区的高峰时间更早，并且流行传播呈现出基于地理接近性的空间扩散模式。相比之下，禽流感显示出较弱的季节性，全年传播较为温和，4 月有一个小高峰（高峰日历周 14.9，95%CI 13.2-17.0），与人类流感高峰不同步。
在孟加拉国，流感预防和控制活动可以根据年度季节性进行安排，在卫生资源规划中应考虑区域异质性。全年的禽流感传播会带来病毒溢出的风险，因此有针对性的努力对于减轻潜在的重组和未来的大流行威胁至关重要。
加拿大卫生研究院范妮·盖尔·韦斯顿博士研究生奖学金。
