Department of Biosciences, Swansea University, Swansea SA2 8PP, UK.
Department of Public Health and Policy, University of Liverpool, Liverpool L69 3GB, UK.
J R Soc Interface. 2020 Dec;17(173):20200775. doi: 10.1098/rsif.2020.0775. Epub 2020 Dec 9.
Controlling the regional re-emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) after its initial spread in ever-changing personal contact networks and disease landscapes is a challenging task. In a landscape context, contact opportunities within and between populations are changing rapidly as lockdown measures are relaxed and a number of social activities re-activated. Using an individual-based metapopulation model, we explored the efficacy of different control strategies across an urban-rural gradient in Wales, UK. Our model shows that isolation of symptomatic cases or regional lockdowns in response to local outbreaks have limited efficacy unless the overall transmission rate is kept persistently low. Additional isolation of non-symptomatic infected individuals, who may be detected by effective test-and-trace strategies, is pivotal to reducing the overall epidemic size over a wider range of transmission scenarios. We define an 'urban-rural gradient in epidemic size' as a correlation between regional epidemic size and connectivity within the region, with more highly connected urban populations experiencing relatively larger outbreaks. For interventions focused on regional lockdowns, the strength of such gradients in epidemic size increased with higher travel frequencies, indicating a reduced efficacy of the control measure in the urban regions under these conditions. When both non-symptomatic and symptomatic individuals are isolated or regional lockdown strategies are enforced, we further found the strongest urban-rural epidemic gradients at high transmission rates. This effect was reversed for strategies targeted at symptomatic individuals only. Our results emphasize the importance of test-and-trace strategies and maintaining low transmission rates for efficiently controlling SARS-CoV-2 spread, both at landscape scale and in urban areas.
控制严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）在不断变化的个人接触网络和疾病格局中的初始传播后的区域性再现是一项具有挑战性的任务。在景观背景下，随着封锁措施的放松和许多社会活动的重新启动，人口内部和之间的接触机会正在迅速变化。我们使用基于个体的复域模型，探索了在英国威尔士的城乡梯度上，不同控制策略的效果。我们的模型表明，除非总体传播率持续保持较低水平，否则针对局部暴发采取隔离症状病例或区域封锁的措施效果有限。通过有效的测试和追踪策略，对无症状感染者进行额外的隔离至关重要，可以在更广泛的传播情景下降低总体疫情规模。我们将“疫情规模的城乡梯度”定义为区域疫情规模与区域内连通性之间的相关性，连通性较高的城市人口会经历相对较大的暴发。对于专注于区域封锁的干预措施，在这些条件下，随着旅行频率的增加，这种疫情规模的梯度强度会增加，表明控制措施在城市地区的效果降低。当隔离无症状和有症状的个体或实施区域封锁策略时，我们还发现，在高传播率下，城乡疫情梯度最强。仅针对有症状个体的策略则产生相反的效果。我们的研究结果强调了测试和追踪策略以及保持低传播率对于在景观和城市地区有效控制 SARS-CoV-2 传播的重要性。
