Measles is a major cause of child mortality in sub-Saharan Africa. Current immunization strategies achieve low coverage in areas where transmission drivers differ substantially from those in high-income countries. A better understanding of measles transmission in areas with measles persistence will increase vaccination coverage and reduce ongoing transmission. We analysed weekly reported measles cases at the district level in Niger from 1995 to 2004 to identify underlying transmission mechanisms. We identified dominant periodicities and the associated spatial clustering patterns. We also investigated associations between reported measles cases and environmental drivers associated with human activities, particularly rainfall. The annual and 2–3-year periodicities dominated the reporting data spectrum. The annual periodicity was strong with contiguous spatial clustering, consistent with the latitudinal gradient of population density, and stable over time. The 2–3-year periodicities were weaker, unstable over time and had spatially fragmented clustering. The rainy season was associated with a lower risk of measles case reporting. The annual periodicity likely reflects seasonal agricultural labour migration, whereas the 2–3-year periodicity potentially results from multiple mechanisms such as reintroductions and vaccine coverage heterogeneity. Our findings suggest that improving vaccine coverage in seasonally mobile populations could reduce strong measles seasonality in Niger and across similar settings.

中文翻译：

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调查尼日尔持续的麻疹动态及其与降雨的关联

麻疹是撒哈拉以南非洲儿童死亡的主要原因。当前的免疫策略在传播驱动因素与高收入国家有很大差异的地区实现了低覆盖率。更好地了解麻疹持续存在地区的麻疹传播将增加疫苗接种覆盖率并减少持续传播。我们分析了 1995 年至 2004 年尼日尔地区级每周报告的麻疹病例，以确定潜在的传播机制。我们确定了主要的周期性和相关的空间聚类模式。我们还调查了报告的麻疹病例与与人类活动（尤其是降雨）相关的环境驱动因素之间的关联。年度和 2-3 年周期主导了报告数据范围。年周期性强，空间聚集连续，与人口密度的纬度梯度一致，且随时间稳定。2-3 年的周期性较弱，随着时间的推移不稳定，并且具有空间分散的聚类。雨季与较低的麻疹病例报告风险相关。年度周期可能反映了季节性农业劳动力迁移，而 2-3 年周期可能是由多种机制造成的，例如重新引入和疫苗覆盖率异质性。我们的研究结果表明，提高季节性流动人口的疫苗覆盖率可以减少尼日尔和类似环境中强烈的麻疹季节性。2-3 年的周期性较弱，随着时间的推移不稳定，并且具有空间分散的聚类。雨季与较低的麻疹病例报告风险相关。年度周期可能反映了季节性农业劳动力迁移，而 2-3 年周期可能是由多种机制造成的，例如重新引入和疫苗覆盖率异质性。我们的研究结果表明，提高季节性流动人口的疫苗覆盖率可以减少尼日尔和类似环境中强烈的麻疹季节性。2-3 年的周期性较弱，随着时间的推移不稳定，并且具有空间分散的聚类。雨季与较低的麻疹病例报告风险相关。年度周期可能反映了季节性农业劳动力迁移，而 2-3 年周期可能是由多种机制造成的，例如重新引入和疫苗覆盖率异质性。我们的研究结果表明，提高季节性流动人口的疫苗覆盖率可以减少尼日尔和类似环境中强烈的麻疹季节性。而 2-3 年的周期可能是由多种机制造成的，例如重新引入和疫苗覆盖的异质性。我们的研究结果表明，提高季节性流动人口的疫苗覆盖率可以减少尼日尔和类似环境中强烈的麻疹季节性。而 2-3 年的周期可能是由多种机制造成的，例如重新引入和疫苗覆盖的异质性。我们的研究结果表明，提高季节性流动人口的疫苗覆盖率可以减少尼日尔和类似环境中强烈的麻疹季节性。