Crucial control measures to contain China's first Delta variant outbreak

Lei Luo; Zifeng Yang; Jingyi Liang; Yu Ma; Hui Wang; Chitin Hon; Mei Jiang; Zhengshi Lin; Wenda Guan; Zhitong Mai; Yongming Li; Kailin Mai; Zhiqi Zeng; Chuanmeizi Tu; Jian Song; Bin Liu; Yong Liu; Jianfeng He; Huiyuan Li; Bosheng Li; Hang Dong; Yutian Miao; Shujun Fan; Lirui Fan; Xingyi Liang; Ke Li; Chun Chen; Huihong Deng; Zhicong Yang; Nanshan Zhong

doi:10.1093/nsr/nwac004

Crucial control measures to contain China's first Delta variant outbreak

Natl Sci Rev. 2022 Jan 18;9(4):nwac004. doi: 10.1093/nsr/nwac004. eCollection 2022 Apr.

Authors

Lei Luo¹, Zifeng Yang², Jingyi Liang², Yu Ma¹, Hui Wang¹, Chitin Hon³, Mei Jiang², Zhengshi Lin², Wenda Guan², Zhitong Mai², Yongming Li², Kailin Mai², Zhiqi Zeng², Chuanmeizi Tu², Jian Song², Bin Liu², Yong Liu², Jianfeng He⁴, Huiyuan Li⁵, Bosheng Li⁴, Hang Dong¹, Yutian Miao¹, Shujun Fan¹, Lirui Fan¹, Xingyi Liang⁶, Ke Li¹, Chun Chen¹, Huihong Deng⁴, Zhicong Yang¹, Nanshan Zhong²

Affiliations

¹ Institute of Public Health, Guangzhou Medical University & Guangzhou Center for Disease Control and Prevention, Guangzhou 510440, China.
² State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China.
³ Macau Institute of Systems Engineering, Macau University of Science and Technology, Taipa 999078, China.
⁴ Guangdong Center for Disease Control and Prevention, Guangzhou 511430, China.
⁵ Kingmed Virology Diagnostic & Translational Center, Guangzhou Kingmed Center for Clinical Laboratory Co., Ltd, Guangzhou 510330, China.
⁶ Department of Urban and Rural Planning, Shunde Urban and Rural Planning Information Research Center, Foshan 528300, China.

Abstract

The SARS-CoV-2 B.1.617.2 (Delta) variant flared up in late May in Guangzhou, China. Transmission characteristics of Delta variant were analysed for 153 confirmed cases and two complete transmission chains with seven generations were fully presented. A rapid transmission occurred in five generations within 10 days. The basic reproduction number (R₀) was 3.60 (95% confidence interval: 2.50-5.30). After redefining the concept of close contact, the proportion of confirmed cases discovered from close contacts increased from 43% to 100%. With the usage of a yellow health code, the potential exposed individuals were self-motivated to take a nucleic acid test and regained public access with a negative testing result. Facing the massive requirement of screening, novel facilities like makeshift inflatable laboratories were promptly set up as a vital supplement and 17 cases were found, with 1 pre-symptomatic. The dynamic adjustment of these three interventions resulted in the decline of Rt from 5.00 to 1.00 within 9 days. By breaking the transmission chain and eliminating the transmission source through extending the scope of the close-contact tracing, health-code usage and mass testing, the Guangzhou Delta epidemic was effectively contained.

Keywords: COVID-19; close contact; control measure; mass testing; public health.