Epstein Adrienne, Aramanzan Okiria, Nabende Isaiah, Kayondo Tonny Max, Obbo Michael, Tumwesigye Robert, Wiringilimaana Innocent, Mbabazi Monica, Kagurusi Brian A, Tukwasibwe Stephen, Ssewanyana Isaac, Routeledge Isobel, Briggs Jessica, Wesolowski Amy, Greenhouse Bryan, Dorsey Grant, Arinaitwe Emmanuel, Rodriguez-Barraquer Isabel
Department of Medicine, University of California San Francisco, San Francisco, California, USA.
Infectious Diseases Research Collaboration, Kampala, Uganda.
medRxiv. 2025 May 15:2025.05.14.25327608. doi: 10.1101/2025.05.14.25327608.
Parasite importation remains a critical challenge to malaria elimination efforts. The extent to which human travel contributes to sustained transmission in low-to-moderate burden areas of highly endemic African countries is poorly understood.
We conducted a 14-month longitudinal cohort study in Kamwezi subcounty in Southwest Uganda, an area targeted for malaria elimination where sustained transmission poses challenges. A total of 1,918 individuals from 400 households were enrolled and followed bi-monthly. Travel histories, malaria episodes, and household characteristics were collected through structured surveys. Incident malaria was captured via passive case detection at the local health facility and self-report. Multilevel logistic regression models estimated the association between overnight travel and incident malaria, adjusting for demographic and household factors. Population attributable fractions (PAF) quantified the contribution of travel to malaria burden, stratified by transmission intensity, season, and village of residence.
Over the study period, 244 malaria episodes were recorded, with incidence highest in villages with greater baseline transmission. Nearly one-third of participants reported at least one overnight trip. We found that associations between travel and malaria varied spatially and temporally, with positive associations in villages of lower transmission (odds ratio=5.65, 95% CI: 2.06-15.45) and during periods of low overall malaria transmission. We found these associations to be strongest for short-distance trips to nearby areas of higher incidence. PAF analyses suggested that travel accounted directly for 17% of malaria cases in low-transmission villages overall, rising to 44.6% during periods of low transmission.
Overnight travel contributed meaningfully to malaria burden, especially in villages with low local burden and during periods of seasonally low transmission. These effects were evident even at small geographic and temporal scales. These findings underscore the importance of malaria surveillance and control strategies that account for both local transmission and travel-related importation, even outside of elimination contexts.
寄生虫输入仍然是疟疾消除工作面临的一项严峻挑战。在非洲高度流行国家的低至中等负担地区，人类旅行对持续传播的影响程度尚不清楚。
我们在乌干达西南部的卡姆韦齐乡进行了一项为期14个月的纵向队列研究，该地区是疟疾消除目标地区，持续传播带来了挑战。共招募了来自400户家庭的1918人，并每两个月进行一次随访。通过结构化调查收集旅行史、疟疾发作情况和家庭特征。通过当地卫生机构的被动病例检测和自我报告来捕获新发疟疾。多水平逻辑回归模型估计过夜旅行与新发疟疾之间的关联，并对人口统计学和家庭因素进行调整。人群归因分数（PAF）量化了旅行对疟疾负担的贡献，并按传播强度、季节和居住村庄进行分层。
在研究期间，记录了244例疟疾发作，发病率在基线传播率较高的村庄最高。近三分之一的参与者报告至少有一次过夜旅行。我们发现旅行与疟疾之间的关联在空间和时间上有所不同，在传播率较低的村庄呈正相关（优势比=5.65，95%置信区间：2.06-15.45），在总体疟疾传播率较低的时期也是如此。我们发现这些关联在前往附近发病率较高地区的短途旅行中最为明显。PAF分析表明，旅行直接导致低传播村庄总体疟疾病例的17%，在传播率较低的时期上升至44.6%。
过夜旅行对疟疾负担有显著贡献，特别是在当地负担较低的村庄和季节性传播率较低的时期。即使在较小的地理和时间尺度上，这些影响也很明显。这些发现强调了疟疾监测和控制策略的重要性，这些策略既要考虑当地传播，也要考虑与旅行相关的输入情况，即使在非消除背景下也是如此。
