Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, 722 West 168th St, New York, NY, 10032, USA.
Nuffield Department of Medicine, University of Oxford, Oxford, UK.
BMC Infect Dis. 2023 Nov 2;23(1):753. doi: 10.1186/s12879-023-08735-6.
Understanding community transmission of SARS-CoV-2 variants of concern (VOCs) is critical for disease control in the post pandemic era. The Delta variant (B.1.617.2) emerged in late 2020 and became the dominant VOC globally in the summer of 2021. While the epidemiological features of the Delta variant have been extensively studied, how those characteristics shaped community transmission in urban settings remains poorly understood.
Using high-resolution contact tracing data and testing records, we analyze the transmission of SARS-CoV-2 during the Delta wave within New York City (NYC) from May 2021 to October 2021. We reconstruct transmission networks at the individual level and across 177 ZIP code areas, examine network structure and spatial spread patterns, and use statistical analysis to estimate the effects of factors associated with COVID-19 spread.
We find considerable individual variations in reported contacts and secondary infections, consistent with the pre-Delta period. Compared with earlier waves, Delta-period has more frequent long-range transmission events across ZIP codes. Using socioeconomic, mobility and COVID-19 surveillance data at the ZIP code level, we find that a larger number of cumulative cases in a ZIP code area is associated with reduced within- and cross-ZIP code transmission and the number of visitors to each ZIP code is positively associated with the number of non-household infections identified through contact tracing and testing.
The Delta variant produced greater long-range spatial transmission across NYC ZIP code areas, likely caused by its increased transmissibility and elevated human mobility during the study period. Our findings highlight the potential role of population immunity in reducing transmission of VOCs. Quantifying variability of immunity is critical for identifying subpopulations susceptible to future VOCs. In addition, non-pharmaceutical interventions limiting human mobility likely reduced SARS-CoV-2 spread over successive pandemic waves and should be encouraged for reducing transmission of future VOCs.
了解 SARS-CoV-2 变异株（VOC）在社区中的传播情况对于大流行后时代的疾病控制至关重要。Delta 变异株（B.1.617.2）于 2020 年末出现，并于 2021 年夏季成为全球主要的 VOC。尽管 Delta 变异株的流行病学特征已得到广泛研究，但这些特征如何影响城市环境中的社区传播仍知之甚少。
利用高分辨率接触者追踪数据和检测记录，我们分析了 2021 年 5 月至 2021 年 10 月期间纽约市（NYC）内 Delta 波期间 SARS-CoV-2 的传播情况。我们在个体和 177 个邮政编码区域层面重建了传播网络，研究了网络结构和空间传播模式，并使用统计分析来估计与 COVID-19 传播相关的因素的影响。
与 Delta 变异株之前的时期相比，报告的接触者和继发感染存在相当大的个体差异。与早期波相比，Delta 波在邮政编码区域之间更频繁地发生长程传播事件。利用邮政编码层面的社会经济、流动性和 COVID-19 监测数据，我们发现邮政编码区域内的累计病例数与减少邮政编码内和跨邮政编码的传播有关，每个邮政编码的访客数量与通过接触者追踪和检测确定的非家庭感染数量呈正相关。
Delta 变异株在整个纽约市邮政编码区域内产生了更大的远程空间传播，这可能是由于其在研究期间的传染性增加和人类流动性增加所致。我们的研究结果强调了人群免疫力在降低 VOC 传播方面的潜在作用。量化免疫的可变性对于识别易受未来 VOC 影响的亚群至关重要。此外，限制人类流动性的非药物干预措施可能减少了连续大流行波中的 SARS-CoV-2 传播，应该鼓励这些措施来减少未来 VOC 的传播。
