Regions of high human population density drive highly localized transmission chains of dengue virus, which then can disperse regionally. Estimating transmission chains for dengue Dengue virus (DENV) causes a large number of asymptomatic infections, so surveillance captures only a fraction of cases. Salje et al. developed a method for identifying the number of transmission chains of DENV from sequence data and serology. They found that sequential transmission of DENV typically occurs between households in the same neighborhood. Within high-density urban localities, such as Bangkok, there are surprisingly few transmission chains. This results in epidemic spikes within a regional background of endemicity. Large urban settings may thus act as a source of diverse viruses that can be transported elsewhere. Science, this issue p. 1302 A fundamental mystery for dengue and other infectious pathogens is how observed patterns of cases relate to actual chains of individual transmission events. These pathways are intimately tied to the mechanisms by which strains interact and compete across spatial scales. Phylogeographic methods have been used to characterize pathogen dispersal at global and regional scales but have yielded few insights into the local spatiotemporal structure of endemic transmission. Using geolocated genotype (800 cases) and serotype (17,291 cases) data, we show that in Bangkok, Thailand, 60% of dengue cases living <200 meters apart come from the same transmission chain, as opposed to 3% of cases separated by 1 to 5 kilometers. At distances <200 meters from a case (encompassing an average of 1300 people in Bangkok), the effective number of chains is 1.7. This number rises by a factor of 7 for each 10-fold increase in the population of the “enclosed” region. This trend is observed regardless of whether population density or area increases, though increases in density over 7000 people per square kilometer do not lead to additional chains. Within Thailand these chains quickly mix, and by the next dengue season viral lineages are no longer highly spatially structured within the country. In contrast, viral flow to neighboring countries is limited. These findings are consistent with local, density-dependent transmission and implicate densely populated communities as key sources of viral diversity, with home location the focal point of transmission. These findings have important implications for targeted vector control and active surveillance.

中文翻译：

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跨时空尺度的登革热多样性：局部结构和宿主种群规模的影响

人口密度高的地区推动登革热病毒高度局部化的传播链，然后可以在区域内分散。估计登革热登革热病毒 (DENV) 的传播链会导致大量无症状感染，因此监测仅捕获了一小部分病例。萨杰等人。开发了一种从序列数据和血清学中识别 DENV 传播链数量的方法。他们发现 DENV 的顺序传播通常发生在同一社区的家庭之间。在曼谷等高密度城市地区，传输链少得惊人。这导致在地方性流行的区域背景下流行病高峰。因此，大型城市环境可能是多种病毒的来源，这些病毒可以传播到其他地方。科学，这个问题 p。1302 登革热和其他传染性病原体的一个基本谜团是观察到的病例模式如何与单个传播事件的实际链相关。这些途径与菌株在空间尺度上相互作用和竞争的机制密切相关。系统地理学方法已被用于表征全球和区域尺度的病原体传播，但对地方性传播的局部时空结构几乎没有深入了解。使用地理定位的基因型（800 例）和血清型（17,291 例）数据，我们表明，在泰国曼谷，生活在 200 米以内的登革热病例中有 60% 来自同一传播链，而相距 1 的病例中只有 3%到 5 公里。在距离案件 <200 米处（曼谷平均 1300 人），链的有效数量为 1.7。“封闭”区域的人口每增加 10 倍，这个数字就会增加 7 倍。无论人口密度或面积是否增加，都会观察到这种趋势，尽管每平方公里 7000 人以上的密度增加不会导致额外的连锁。在泰国，这些连锁店迅速混合，到下一个登革热季节，病毒谱系在该国内不再具有高度的空间结构。相比之下，病毒流向邻国是有限的。这些发现与本地的、依赖于密度的传播一致，并暗示人口稠密的社区是病毒多样性的主要来源，而家庭所在地是传播的焦点。这些发现对有针对性的病媒控制和主动监测具有重要意义。