Seasonality of influenza in Brazil: A traveling wave from the Amazon to the subtropics
Seasonality of influenza in Brazil: A traveling wave from the Amazon to the subtropics
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DOI：
10.1093/aje/kwm012
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发表时间：
2007-06-15
影响因子：
5
通讯作者：
Miller, Mark A.
中科院分区：
文献类型：
--
作者：
Alonso, Wladimir J.;Viboud, Cecile;Miller, Mark A.
热带地区的流感传播和死亡影响尚未得到很好的描述。作者通过模拟流感相关死亡率和实验室监测数据，研究了巴西这个地理上多样化的国家流感的季节性。从1979年至2001年，获得了巴西27个州每个州肺炎和流感死亡率的每月时间序列。对剔除趋势的时间序列进行傅立叶分解，以描述年度和半年流行周期的幅度和时间，并将所产生的季节参数在从赤道(北纬+5度)到亚热带(S度-35度)的范围内进行比较。死亡率的季节性在南部各州(冬季流行，6-7月)最为明显，向中部各州(S 15度)逐渐减弱(p<；0.001)，并在赤道附近保持较低水平。在巴西各地发现了一波季节性的向南传播的流感浪潮，从3-4月开始，从赤道和低人口地区开始，在3个月的时间里向温带和人口稠密地区扩散。最近几年的实验室监测数据独立证实，死亡高峰与流感病毒活动相吻合。传播波的方向表明，环境因素(温度、湿度)在推动巴西全国流感流行时间方面发挥着比人口因素(密度、旅行)更重要的作用。
Influenza circulation and mortality impact in tropical areas have not been well characterized. The authors studied the seasonality of influenza throughout Brazil, a geographically diverse country, by modeling influenza-related mortality and laboratory surveillance data. Monthly time series of pneumonia and influenza mortality were obtained from 1979 to 2001 for each of the 27 Brazilian states. Detrended time series were analyzed by Fourier decomposition to describe the amplitude and timing of annual and semiannual epidemic cycles, and the resulting seasonal parameters were compared across latitudes, ranging from the equator (+5 degrees N) to the subtropics (-35 degrees S). Seasonality in mortality was most pronounced in southern states (winter epidemics, June-July), gradually attenuated toward central states (15 degrees S) (p < 0.001), and remained low near the equator. A seasonal southward traveling wave of influenza was identified across Brazil, originating from equatorial and low-population regions in March-April and moving toward temperate and highly populous regions over a 3-month period. Laboratory surveillance data from recent years provided independent confirmation that mortality peaks coincided with influenza virus activity. The direction of the traveling wave suggests that environmental forces (temperature, humidity) play a more important role than population factors (density, travel) in driving the timing of influenza epidemics across Brazil.