Parametric analysis of the transmission dynamics during indigenous aggregated outbreaks caused by five SARS-CoV-2 strains in Nanjing, China

Tao Ma; Cong Chen; Junjun Wang; Hengxue Wang; Yueyuan Zhao; Yuanzhao Zhu; Zikang Yan; Songning Ding; Jie Ding

doi:10.3389/fpubh.2024.1358577

Parametric analysis of the transmission dynamics during indigenous aggregated outbreaks caused by five SARS-CoV-2 strains in Nanjing, China

Front Public Health. 2024 Mar 8:12:1358577. doi: 10.3389/fpubh.2024.1358577. eCollection 2024.

Authors

Tao Ma^#¹, Cong Chen^#^{2

3}, Junjun Wang¹, Hengxue Wang¹, Yueyuan Zhao¹, Yuanzhao Zhu¹, Zikang Yan¹, Songning Ding¹, Jie Ding¹

Affiliations

¹ Department of Acute Infectious Diseases Control and Prevention, Nanjing Municipal Center for Disease Control and Prevention, Nanjing, China.
² Wujin District Center for Disease Control and Prevention, Changzhou, China.
³ Jiangsu Field Epidemiology Training Program, Jiangsu Provincial Centre for Disease Control and Prevention, Nanjing, China.

^# Contributed equally.

Abstract

Background: SARS-CoV-2 strains have been of great concern due to their high infectivity and antibody evasion.

Methods: 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 (R₀), and the household secondary attack rate (HSAR). Finally, we compared the trends of transmission dynamic parameters of different strains.

Results: 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 (p < 0.001); Moreover, R₀ 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 (p < 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 (p < 0.001).

Conclusion: Compared to the original strain, the incubation period and SI decreased while R₀ 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.

Keywords: COVID-19; SARS-CoV-2; indigenous aggregated outbreaks; parametric analysis; transmission dynamics.

MeSH terms

COVID-19* / epidemiology
China / epidemiology
Disease Outbreaks
Humans
SARS-CoV-2*

Supplementary concepts

SARS-CoV-2 variants

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. The Project of Nanjing Health Science and Technology Development (YKK22190) and Nanjing Key Medical Subject (Infectious Disease Prevention and Control).