Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.
Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States.
PLoS Negl Trop Dis. 2020 Apr 15;14(4):e0008227. doi: 10.1371/journal.pntd.0008227. eCollection 2020 Apr.
The global burden of cholera is increasing, with the majority (60%) of the cases occurring in sub-Saharan Africa. In Zambia, widespread cholera outbreaks have occurred since 1977, predominantly in the capital city of Lusaka. During both the 2016 and 2018 outbreaks, the Ministry of Health implemented cholera vaccination in addition to other preventative and control measures, to stop the spread and control the outbreak. Given the limitations in vaccine availability and the logistical support required for vaccination, oral cholera vaccine (OCV) is now recommended for use in the high risk areas ("hotspots") for cholera. Hence, the aim of this study was to identify areas with an increased risk of cholera in Zambia. Retrospective cholera case data from 2008 to 2017 was obtained from the Ministry of Health, Department of Public Health and Disease Surveillance. The Zambian Central Statistical Office provided district-level population data, socioeconomic and water, sanitation and hygiene (WaSH) indicators. To identify districts at high risk, we performed a discrete Poisson-based space-time scan statistic to account for variations in cholera risk across both space and time over a 10-year study period. A zero-inflated negative binomial regression model was employed to identify the district level risk factors for cholera. The risk map was generated by classifying the relative risk of cholera in each district, as obtained from the space-scan test statistic. In total, 34,950 cases of cholera were reported in Zambia between 2008 and 2017. Cholera cases varied spatially by year. During the study period, Lusaka District had the highest burden of cholera, with 29,080 reported cases. The space-time scan statistic identified 16 districts to be at a significantly higher risk of having cholera. The relative risk of having cholera in these districts was significantly higher and ranged from 1.25 to 78.87 times higher when compared to elsewhere in the country. Proximity to waterbodies was the only factor associated with the increased risk for cholera (P<0.05). This study provides a basis for the cholera elimination program in Zambia. Outside Lusaka, the majority of high risk districts identified were near the border with the DRC, Tanzania, Mozambique, and Zimbabwe. This suggests that cholera in Zambia may be linked to movement of people from neighboring areas of cholera endemicity. A collaborative intervention program implemented in concert with neighboring countries could be an effective strategy for elimination of cholera in Zambia, while also reducing rates at a regional level.
霍乱的全球负担正在增加，其中 60%的病例发生在撒哈拉以南非洲地区。在赞比亚，自 1977 年以来，广泛的霍乱爆发一直发生，主要集中在首都卢萨卡。在 2016 年和 2018 年的疫情中，卫生部除了采取其他预防和控制措施外，还实施了霍乱疫苗接种，以阻止疫情传播和控制疫情。鉴于疫苗供应的限制以及疫苗接种所需的后勤支持，口服霍乱疫苗（OCV）现在建议在霍乱高危地区（“热点地区”）使用。因此，本研究旨在确定赞比亚霍乱高风险地区。从卫生部公共卫生和疾病监测司获得了 2008 年至 2017 年的回顾性霍乱病例数据。赞比亚中央统计局提供了地区一级的人口数据、社会经济以及水、环境卫生和个人卫生（WASH）指标。为了确定高风险地区，我们使用离散泊松时空扫描统计数据来考虑 10 年研究期间空间和时间上霍乱风险的变化。使用零膨胀负二项回归模型来确定霍乱的地区一级风险因素。风险图是通过对每个地区的霍乱相对风险进行分类生成的，该风险是从时空扫描检验统计数据中获得的。2008 年至 2017 年间，赞比亚共报告了 34950 例霍乱病例。霍乱病例在空间上随年份而变化。在研究期间，卢萨卡地区的霍乱负担最重，报告病例 29080 例。时空扫描统计数据确定了 16 个地区发生霍乱的风险显著更高。这些地区发生霍乱的相对风险明显更高，与该国其他地区相比，风险范围为 1.25 至 78.87 倍。靠近水体是唯一与霍乱风险增加相关的因素（P<0.05）。本研究为赞比亚的霍乱消除计划提供了依据。在卢萨卡以外，确定的大多数高风险地区都靠近与刚果民主共和国、坦桑尼亚、莫桑比克和津巴布韦的边界。这表明赞比亚的霍乱可能与来自霍乱流行地区的人员流动有关。与邻国实施协作干预计划可能是赞比亚消除霍乱的有效策略，同时也可以降低区域层面的发病率。
