Washington State University Global Health Program-Kenya, Nairobi, Kenya.
University of Nairobi, Faculty of Health Sciences, Nairobi, Kenya.
BMJ Glob Health. 2024 Jun 10;9(6):e014737. doi: 10.1136/bmjgh-2023-014737.
Recent epidemiology of Rift Valley fever (RVF) disease in Africa suggests growing frequency and expanding geographic range of small disease clusters in regions that previously had not reported the disease. We investigated factors associated with the phenomenon by characterising recent RVF disease events in East Africa.
Data on 100 disease events (2008-2022) from Kenya, Uganda and Tanzania were obtained from public databases and institutions, and modelled against possible geoecological risk factors of occurrence including altitude, soil type, rainfall/precipitation, temperature, normalised difference vegetation index (NDVI), livestock production system, land-use change and long-term climatic variations. Decadal climatic variations between 1980 and 2022 were evaluated for association with the changing disease pattern.
Of 100 events, 91% were small RVF clusters with a median of one human (IQR, 1-3) and three livestock cases (IQR, 2-7). These clusters exhibited minimal human mortality (IQR, 0-1), and occurred primarily in highlands (67%), with 35% reported in areas that had never reported RVF disease. Multivariate regression analysis of geoecological variables showed a positive correlation between occurrence and increasing temperature and rainfall. A 1°C increase in temperature and a 1-unit increase in NDVI, one months prior were associated with increased RVF incidence rate ratios of 1.20 (95% CI 1.1, 1.2) and 1.93 (95% CI 1.01, 3.71), respectively. Long-term climatic trends showed a significant decadal increase in annual mean temperature (0.12-0.3°C/decade, p<0.05), associated with decreasing rainfall in arid and semi-arid lowlands but increasing rainfall trends in highlands (p<0.05). These hotter and wetter highlands showed increasing frequency of RVF clusters, accounting for 76% and 43% in Uganda and Kenya, respectively.
These findings demonstrate the changing epidemiology of RVF disease. The widening geographic range of disease is associated with climatic variations, with the likely impact of wider dispersal of virus to new areas of endemicity and future epidemics.
非洲裂谷热（RVF）疾病的最近流行病学情况表明，在以前未报告该疾病的地区，小疾病群的发生频率和地理范围不断扩大。我们通过描述东非最近的 RVF 疾病事件来研究与这种现象相关的因素。
从公共数据库和机构获取了肯尼亚、乌干达和坦桑尼亚的 100 个疾病事件（2008-2022 年）的数据，并针对包括海拔、土壤类型、降雨/降水、温度、归一化差异植被指数（NDVI）、牲畜生产系统、土地利用变化和长期气候变化在内的可能地理生态发生因素进行建模。评估了 1980 年至 2022 年期间的十年气候变化与疾病模式变化的关联。
在 100 个事件中，91%为 RVF 小集群，中位数为 1 例人类病例（IQR，1-3）和 3 例牲畜病例（IQR，2-7）。这些集群的人类死亡率很低（IQR，0-1），主要发生在高地（67%），其中 35%报告发生在从未报告过 RVF 疾病的地区。地理生态变量的多变量回归分析显示，发生与温度升高和降雨增加呈正相关。与 RVF 发病率比相关的一个月前温度升高 1°C 和 NDVI 增加 1 个单位分别为 1.20（95%CI 1.1, 1.2）和 1.93（95%CI 1.01, 3.71）。长期气候趋势显示，年平均气温呈显著的十年间增加（0.12-0.3°C/十年，p<0.05），与干旱和半干旱低地的降雨量减少相关，但与高地的降雨量增加趋势相关（p<0.05）。这些较热和较湿润的高地显示出 RVF 集群的发生频率增加，乌干达和肯尼亚分别占 76%和 43%。
这些发现表明 RVF 疾病的流行病学情况正在发生变化。疾病地理范围的扩大与气候变化有关，可能导致病毒向新的流行地区更广地传播，并引发未来的疫情。
