Optimising passive surveillance of a neglected tropical disease in the era of elimination: A modelling study

背景：监测是消除传染病和避免（再）新发疾病流行计划的重要组成部分。随着病例数量的下降，治疗和控制费用减少，但监测费用即使在出现“最后”病例之后仍然很高。减少监测可能会有漏掉持续存在或（重新）出现的疾病疫源地的风险。在这里，我们使用基于模拟的方法来确定确保最大限度地覆盖传染病风险人群（PAR）所需的最小被动监测点数量。在本研究中，我们以乌干达西北部的冈比亚人类非洲锥虫病（g-HAT）为例，这是一种被忽视的热带病（NTD），已降至历史最低水平（全球每年<1000例）。为了量化到诊断设施的旅行时间（监测覆盖范围的代表），我们制作了一个高空间分辨率的阻力面，并进行了成本-距离分析。我们模拟了具有不同数量和位置的诊断设施的PAR的旅行时间，根据国内目标量化了1小时和5小时旅行内PAR的百分比。我们的模拟表明，即使在偏远地区，诊断中心70%的减少（51/170）仍然超过了覆盖的最低目标，约300万人的总PAR中有95%的人距离诊断中心的生活时间不超过1小时。结论：研究结果强调，在乌干达西北部可缩减对g-HAT的监测，而不会大幅减少PAR的覆盖率。所描述的方法有助于制定具有成本效益和公平的战略，以监测被忽视的热带病和其他即将消除或（重新）出现的传染病。

BackgroundSurveillance is an essential component of programs to eliminate infectious diseases and avert epidemics of (re-)emerging diseases. As the numbers of cases decline, costs of treatment and control diminish but those for surveillance remain high even after the 'last' case. Reducing surveillance may risk missing persistent or (re-)emerging foci of disease. Here, we use a simulation-based approach to determine the minimal number of passive surveillance sites required to ensure maximum coverage of a population at-risk (PAR) of an infectious disease.Methodology and principal findingsFor this study, we use Gambian human African trypanosomiasis (g-HAT) in north-western Uganda, a neglected tropical disease (NTD) which has been reduced to historically low levels (<1000 cases/year globally), as an example. To quantify travel time to diagnostic facilities, a proxy for surveillance coverage, we produced a high spatial-resolution resistance surface and performed cost-distance analyses. We simulated travel time for the PAR with different numbers and locations of diagnostic facilities, quantifying the percentage of the PAR within 1h and 5h travel, as per in-country targets. Our simulations indicate that a 70% reduction (51/170) in diagnostic centres still exceeded minimal targets of coverage even for remote populations, with >95% of a total PAR of ~3million individuals living 1h or less from a diagnostic centre.ConclusionsOur results highlight that surveillance of g-HAT in north-western Uganda can be scaled back without substantially reducing coverage of the PAR. The methodology described can contribute to cost-effective and equitable strategies for the surveillance of NTDs and other infectious diseases approaching elimination or (re-)emergence.