The SARS-CoV-2 Delta variant of concern spread globally, causing resurgences of COVID-19 worldwide^1,2. Delta’s emergence in the UK occurred on the background of a heterogeneous landscape of immunity and relaxation of non-pharmaceutical interventions. Here we analyse 52,992 virus genomes from England together with 93,649 global genomes to reconstruct the emergence of Delta, and quantify its introduction to and regional dissemination across England in the context of changing travel and social restrictions. Through analysis of human movement, contact tracing, and virus genomic data, we find that the geographic focus of Delta’s expansion shifted from India to a more global pattern in early May 2021. In England, Delta lineages were introduced >1,000 times and spread nationally as non-pharmaceutical interventions were relaxed. We find that hotel quarantine for travellers reduced onward transmission from importations; however transmission chains that later dominated England’s Delta wave were seeded before travel restrictions were introduced. Increasing inter-regional travel within England drove Delta's nationwide dissemination, with some cities receiving >2,000 observable lineage introductions from elsewhere. Subsequently, increased levels of local population mixing, not the number of importations, were associated with faster relative growth of Delta. Delta’s invasion dynamics depended on spatial heterogeneity in contact patterns, and our findings will inform optimal spatial interventions to reduce transmission of current and future variant of concern, such as Omicron.

值得关注的 SARS-CoV-2 Delta 变种在全球范围内传播，导致 COVID-19 在全球范围内卷土重来^1​​,2。达美航空在英国的出现是在免疫的异质格局和非药物干预措施放松的背景下发生的。在这里，我们分析了来自英格兰的 52,992 个病毒基因组以及 93,649 个全球基因组，以重建三角洲病毒的出现，并在旅行和社会限制不断变化的背景下量化其在英格兰的引入和区域传播。通过对人类活动、接触者追踪和病毒基因组数据的分析，我们发现 Delta 扩张的地理重点在 2021 年 5 月上旬从印度转向了更加全球化的模式。在英格兰，Delta 谱系被引入超过 1,000 次，并在全国范围内传播非药物干预有所放松。我们发现，对旅客进行酒店隔离减少了输入性传播；然而，后来主导英格兰三角洲浪潮的传输链是在旅行限制出台之前就已经播种的。英格兰境内越来越多的跨地区旅行推动了达美航空在全国范围内的传播，一些城市从其他地方接收了超过 2,000 个可观察到的血统介绍。随后，当地人口混合水平的提高，而不是输入的数量，与三角洲较快的相对增长有关。Delta 的入侵动态取决于接触模式的空间异质性，我们的研究结果将为最佳空间干预措施提供信息，以减少当前和未来关注变体（例如 Omicron）的传播。