Department of Medicine, University of California, San Diego, CA 92093, USA.
Veterans Affairs Health System, San Diego, CA 92093, USA.
Viruses. 2022 Jul 8;14(7):1494. doi: 10.3390/v14071494.
Evolutionary analysis using viral sequence data can elucidate the epidemiology of transmission. Using publicly available SARS-CoV-2 sequence and epidemiological data, we developed discrete phylogeographic models to interrogate the emergence and dispersal of the Delta and Omicron variants in 2021 between and across California and Mexico. External introductions of Delta and Omicron in the region peaked in early July (2021-07-10 [95% CI: 2021-04-20, 2021-11-01]) and mid-December (2021-12-15 [95% CI: 2021-11-14, 2022-01-09]), respectively, 3 months and 2 weeks after first detection. These repeated introductions coincided with domestic migration events with no evidence of a unique transmission hub. The spread of Omicron was most consistent with gravity centric patterns within Mexico. While cross-border events accounted for only 5.1% [95% CI: 4.3-6] of all Delta migration events, they accounted for 20.6% [95% CI: 12.4-29] of Omicron movements, paralleling the increase in international travel observed in late 2021. Our investigations of the Delta and Omicron epidemics in the California/Mexico region illustrate the complex interplay and the multiplicity of viral and structural factors that need to be considered to limit viral spread, even as vaccination is reducing disease burden. Understanding viral transmission patterns may help intra-governmental responses to viral epidemics.
利用病毒序列数据进行进化分析可以阐明传播的流行病学。我们使用公开的 SARS-CoV-2 序列和流行病学数据，开发了离散的系统地理学模型，以研究 2021 年加利福尼亚州和墨西哥之间和内部的 Delta 和奥密克戎变体的出现和传播。该地区 Delta 和奥密克戎的外部传入高峰分别出现在 2021 年 7 月 10 日（95%CI：2021-04-20，2021-11-01）和 2021 年 12 月 15 日（95%CI：2021-11-14，2022-01-09），即首次检测后 3 个月和 2 周。这些重复的传入事件与国内迁移事件同时发生，没有证据表明存在独特的传播中心。奥密克戎的传播最符合墨西哥内的重力中心模式。虽然跨境事件仅占 Delta 迁移事件的 5.1%[95%CI：4.3-6]，但占奥密克戎传播的 20.6%[95%CI：12.4-29]，与 2021 年末观察到的国际旅行增加相吻合。我们对加利福尼亚州/墨西哥地区的 Delta 和奥密克戎流行的调查说明了病毒和结构因素的复杂相互作用和多样性，即使疫苗接种正在降低疾病负担，也需要考虑这些因素来限制病毒传播。了解病毒传播模式可能有助于政府间对病毒流行的应对。
