目的：探讨某独栋办公楼内新型冠状病毒（新冠）奥密克戎株感染疫情的传播特点和防控策略。方法：回顾性收集2022年3月19日至3月28日期间该办公楼内458名风险人群中新冠奥密克戎株的感染率、流调情况、传播链、人群疫苗接种情况以及感染病例的核酸循环阈值（cycle threshold,Ct值）等数据,并记录所采取的应对措施和转归情况,分析本轮疫情的传播特点,并总结防控策略。结果：某办公楼内的疫情从3月19日发生第1例新冠感染到3月28日清零,共计10 d。办公楼内458名人员中,累计感染人数达42例,感染率为9.17%。在3月21日对重点人群进行单间隔离后,发病率明显下降,逆转了之前的感染上升态势。新冠奥密克戎株的实时传播指数（real-time reproduction number, Rt）值随时间发生动态变化,从10.8迅速下降为2.2,隔离第3天即低于1。Ct值在30以上的患者,与其密切接触者（密接）转阳率约为6.0%;Ct值在20~30之间的患者,密接者转阳率较高,为25.6%;Ct值在20以下的患者,密接者转阳率高达62.5%。与Ct值>30的病例及其对应的密接相比,病例Ct值为20~30感染者的密接其感染风险显著上升（OR=5.37,95%CI：1.88~15.33）;病例Ct值<20感染者的密接者其感染风险则进一步上升（OR=25.95,95%CI：9.11~73.94）。结论：新冠病毒传播力与传播者的核酸Ct值水平密切相关,对于Ct值较低者应考虑优先予以转运治疗,并对其密接人员进行优先隔离处理。根据感染者的Ct值进行精细化管理,对避免病毒在社区中暴发具有重要意义。

Objective: To explore the epidemic spread and prevention strategy of COVID-19 by Omicron variant in a single office building. Methods: Retrospective data were collected for the period from March 19, 2022 to March 28, 2022. During this period, the infection rate, epidemic survey, transmission chain, population vaccination and Ct value of infected cases, as well as other data of 458 persons at risk in the single office building were collected. The response measures and outcomes were recorded, and the characteristics of this round of epidemic transmission were analyzed, and the prevention and control strategies were summarized. Results: The epidemic situation in a single office building lasted for 10 days from March 19 to March 28. Forty-two out of the 458 persons in the office building were infected, with an infection rate of 9.17%. After the large-scale single room isolation measure was put in place for key populations on March 21, the infection rate showed a significant downward trend, reversing the previous upward trend. The real-time reproduction number (Rt) value changed dynamically with time (from 10.8 to 2.2) and reached a value of lower than 1 on the third day of isolation. For patients with Ct value above 30, the positive conversion rate of close contacts was about 6.0%. For patients with Ct value between 20-30, the positive conversion rate of close contacts is higher, about 25.6%. Among patients with Ct value below 20, the conversion rate of close contacts was as high as 62.5%. Compared with CT value >30 and their corresponding close contacts as the reference group, the infection risk of close contacts of infected persons with CT value of 20-30 increased significantly (OR=5.37, 95% CI: 1.88-15.33). The infection risk of close contacts of infected persons with CT value <20 increased further (OR=25.95, 95% CI: 9.11-73.94). Conclusions: The transmission power of the variant of SARS-coV-2is closely related to the level of nucleic acid Ct value of the disseminator. For those with low Ct value, priority should be given to transport treatment, and their close contacts should be isolated. Fine management according to the Ct value of the infected person may play a great role in blocking the high-risk transmission chain of the disease and may be of great significance to avoid the outbreak of the virus in the community.