Greene Sharon K, Ionides Edward L, Wilson Mark L
Department of Epidemiology, University of Michigan, Ann Arbor, MI, USA.
Am J Epidemiol. 2006 Feb 15;163(4):316-26. doi: 10.1093/aje/kwj040. Epub 2006 Jan 4.
The regular seasonality of influenza in temperate countries is recognized, but regional differences in patterns of influenza-related mortality are poorly understood. Identifying patterns could improve epidemic prediction and prevention. The authors analyzed the monthly percentage of deaths attributable to pneumonia and influenza among people aged 65 or more years in the contiguous United States, 1968-1998. The local Moran's I test for spatial autocorrelation and correlograms assessing space-time synchrony within each influenza season were applied to detect and to characterize mortality patterns. Western US regions experienced epidemics of greater magnitude than did eastern regions. Positive spatial autocorrelation (two-sided p = 0.001) revealed the similarity in influenza mortality of neighboring states, with several western states forming a focus of high mortality. In transmission seasons dominated by virus subtype A(H3N2), mortality was correlated at a high and consistent level across the United States (mean correlation = 0.56, standard deviation = 0.134). However, when subtype A(H1N1) or type B dominated, the average synchrony was lower (mean correlation = 0.23, standard deviation = 0.058). These novel analyses suggest that causes of spatial heterogeneity (e.g., large-scale environmental drivers and population movement) have impacted influenza-associated mortality.
温带国家流感的季节性规律已为人所知，但人们对流感相关死亡率模式的地区差异了解甚少。识别这些模式有助于改善疫情预测和预防。作者分析了1968年至1998年美国本土65岁及以上人群中因肺炎和流感导致的死亡月度百分比。运用局部莫兰指数空间自相关检验以及评估每个流感季节内时空同步性的相关图来检测和描述死亡率模式。美国西部地区的疫情规模比东部地区更大。正空间自相关（双侧p = 0.001）揭示了相邻州流感死亡率的相似性，几个西部州形成了高死亡率的聚集区。在以A(H3N2)病毒亚型为主导的传播季节，全美国的死亡率呈现高度且一致的相关性（平均相关性 = 0.56，标准差 = 0.134）。然而，当A(H1N1)亚型或B型为主导时，平均同步性较低（平均相关性 = 0.23，标准差 = 0.058）。这些新的分析表明，空间异质性的成因（如大规模环境驱动因素和人口流动）对流感相关死亡率产生了影响。
