Infectious Disease Surveillance Center, National Institute of Infectious Diseases, Tokyo, Japan. inaida＠nih.go.jp
Jpn J Infect Dis. 2011;64(6):473-81.
The identification of geographic trends of an influenza pandemic is important for analyzing its social epidemic factors. We performed spatiotemporal analyses focusing on the metropolitan areas in Japan by using the influenza-like illness (ILI) sentinel surveillance data for the pandemic (H1N1) 2009 and seasonal influenza. The epidemic curves and spread features expressed by the kriging method of geographic information system (GIS) and correlations between reported cases and demographic data were analyzed. The incidence of pandemic (H1N1) 2009 increased gradually at the beginning and showed more sporadic epidemic features compared to seasonal influenza. However, there were coincidental locations of patient clusters affected by the seasonal influenza, with a significant coefficient for the total sentinel reported cases (r = 0.71, P < 0.01). This suggested similar patterns of the epidemic over seasons. Patient clusters tended to be located in suburban areas, and there seemed to be stronger relationships between epidemics and higher ratio of larger families (with r = 0.26-0.35, P < 0.01, between ratio of families having more than 3 members and total reported cases in Tokyo and Nagoya areas). Whether populous areas had a greater probability of maintaining the epidemic patterns needs to be determined. Nonetheless, the patterns found in this study can be useful for further analyses for epidemic modeling and designing relevant controls.
流感大流行的地理趋势的识别对于分析其社会流行因素很重要。我们使用流感样疾病（ILI）哨点监测数据对大流行（H1N1）2009 年和季节性流感进行时空分析，重点关注日本的大都市区。我们分析了地理信息系统（GIS）的克里金方法表示的流行曲线和传播特征，以及报告病例与人口数据之间的相关性。大流行（H1N1）2009 年的发病率起初逐渐增加，与季节性流感相比，具有更多的散发性流行特征。然而，季节性流感患者集群的发病地点存在巧合，与总哨点报告病例具有显著相关性（r = 0.71，P < 0.01）。这表明季节之间存在相似的流行模式。患者集群倾向于位于郊区，并且疫情与大家庭比例（与东京和名古屋地区的总报告病例之间的 r = 0.26-0.35，P < 0.01）之间似乎存在更强的关系。人口稠密地区是否更有可能维持流行模式仍需确定。尽管如此，本研究中发现的模式对于进一步进行流行建模和设计相关控制措施的分析可能是有用的。
