Department of Acute Infectious Diseases Control and Prevention, Nanjing Municipal Center for Disease Control and Prevention, Nanjing, China.
Wujin District Center for Disease Control and Prevention, Changzhou, China.
Front Public Health. 2024 Mar 8;12:1358577. doi: 10.3389/fpubh.2024.1358577. eCollection 2024.
SARS-CoV-2 strains have been of great concern due to their high infectivity and antibody evasion.
In this study, data were collected on indigenous aggregated outbreaks in Nanjing from January 2020 to December 2022, caused by five strains including the original strain, the Delta variant, and the Omicron variant (BA.2, BA.5.2, and BF.7). The basic epidemiological characteristics of infected individuals were described and then parametric analysis of transmission dynamics was performed, including the calculation of incubation period, serial interval (SI), the basic reproductive number (R), and the household secondary attack rate (HSAR). Finally, we compared the trends of transmission dynamic parameters of different strains.
The incubation period for the original strain, the Delta variant, Omicron BA.2, Omicron BA.5.2, and Omicron BF.7 were 6 d (95% CI: 3.5-7.5 d), 5 d (95% CI: 4.0-6.0 d), 3 d (95% CI: 3.0-4.0 d), 3 d (95% CI: 3.0-3.0 d), and 2 d (95% CI: 2.0-3.0 d), respectively; Also, the SI of the five strains were 5.69 d, 4.79 d, 2.7 d, 2.12 d, and 2.43 d, respectively. Notably, the incubation period and SI of the five had both a progressive shortening trend ( < 0.001); Moreover, R of the five were 2.39 (95% CI: 1.30-4.29), 3.73 (95% CI: 2.66-5.15), 5.28 (95% CI: 3.52-8.10), 5.54 (95% CI: 2.69-11.17), 7.39 (95% CI: 2.97-18.76), with an increasing trend gradually ( < 0.01); HSAR of the five were 25.5% (95% CI: 20.1-31.7%), 27.4% (95% CI: 22.0-33.4%), 42.9% (95% CI: 34.3-51.8%), 53.1% (95% CI: 45.0-60.9%), 41.4% (95% CI, 25.5-59.3%), also with an increasing trend ( < 0.001).
Compared to the original strain, the incubation period and SI decreased while R and HSAR increased, suggesting that transmission in the population was faster and the scope of the population was wider. Overall, it's crucial to keep implementing comprehensive measures like monitoring and alert systems, herd immunization plans, and outbreak control.
由于 SARS-CoV-2 变异株具有高传染性和抗体逃逸能力，因此一直备受关注。
本研究收集了 2020 年 1 月至 2022 年 12 月期间南京发生的 5 种毒株（包括原始株、Delta 变异株和奥密克戎变异株（BA.2、BA.5.2 和 BF.7）引起的本地聚集性疫情数据。描述了感染者的基本流行病学特征，然后对传播动力学进行参数分析，包括潜伏期、序列间隔（SI）、基本繁殖数（R）和家庭二次攻击率（HSAR）的计算。最后，我们比较了不同毒株传播动态参数的趋势。
原始株、Delta 变异株、奥密克戎 BA.2、奥密克戎 BA.5.2 和奥密克戎 BF.7 的潜伏期分别为 6d（95%CI：3.5-7.5d）、5d（95%CI：4.0-6.0d）、3d（95%CI：3.0-4.0d）、3d（95%CI：3.0-3.0d）和 2d（95%CI：2.0-3.0d）；此外，这 5 种毒株的 SI 分别为 5.69d、4.79d、2.7d、2.12d 和 2.43d。值得注意的是，这 5 种毒株的潜伏期和 SI 均呈渐进缩短趋势（ < 0.001）；此外，这 5 种毒株的 R 值分别为 2.39（95%CI：1.30-4.29）、3.73（95%CI：2.66-5.15）、5.28（95%CI：3.52-8.10）、5.54（95%CI：2.69-11.17）和 7.39（95%CI：2.97-18.76），呈逐渐增加趋势（ < 0.01）；这 5 种毒株的 HSAR 分别为 25.5%（95%CI：20.1-31.7%）、27.4%（95%CI：22.0-33.4%）、42.9%（95%CI：34.3-51.8%）、53.1%（95%CI：45.0-60.9%）和 41.4%（95%CI，25.5-59.3%），也呈上升趋势（ < 0.001）。
与原始株相比，潜伏期和 SI 缩短，而 R 和 HSAR 增加，提示人群中的传播速度更快，人群范围更广。总的来说，必须继续实施综合措施，如监测和警报系统、群体免疫计划和疫情控制。
