Impact of public health and social measures on contact dynamics during a SARS-CoV-2 Omicron variant outbreak in Quanzhou, China, March to April 2022. (June 2023)

• Record Type: Journal Article
• Authors: Guo, Yichao; Wu, Shenggen; Ye, Wenjing; Zhao, Zeyu; Li, Kangguo; Guo, Xiaohao; Chen, Wu; Cai, Shaojian; Zhan, Meirong; Huang, Zhengqiang; Ou, Jianming; Chen, Tianmu
• Is Part Of: International journal of infectious diseases. Volume 131(2023)
• Page Start: 46
• Page End: 49
• Publication Date: 2023-06
• Subjects: COVID-19 -- Contact tracing -- Public health intervention; Communicable diseases -- Periodicals; Communicable Diseases -- Periodicals; Communicable diseases; Periodicals; Electronic journals; 616.9
• DOI: 10.1016/j.ijid.2023.03.025
• Languages: English
• ISSNs: 1201-9712

Abstract

Highlights: A total of 66, 583 close contacts were included to estimate contact patterns. Interventions reduce contact in public but increase contact within households. Asymptomatic cases account for over 65% of cases with a high number of contacts. Asymptomatic cases make up over 80% of cases that caused a high number of secondary cases. Abstract: Objectives: To evaluate the impact of early implementation of public health and social measures (PHSMs) on contact rates over time and explore contact behavior of asymptomatic versus symptomatic cases. Methods: We used the largest contact tracing data in China thus far to estimate the mean contacts over time by age groups and contact settings. We used bootstrap with replacement to quantify the uncertainty of contact matrixes. The Pearson correlation was performed to demonstrate the number of contacts over time in relation to the evolution of restrictions. In addition, we analyzed the index cases with a high number of contacts and index cases that produced a high number of secondary cases. Results: Rapidly adapted PHSMs can reduce the mean contact rates in public places while increasing the mean contact rates within households. The mean contact rates were 11.81 (95% confidence interval, 11.61-12.01) for asymptomatic (at the time of investigation) cases and 6.70 (95% confidence interval, 6.54-6.87) for symptomatic cases. The percentage of asymptomatic cases (at the time of investigation) meeting >50 close contacts make up more than 65% of the overall cases. The percentage of asymptomatic cases producing >10 secondary cases account for more than 80% of the overall cases. Conclusion: PHSMs may increase the contacts within the household, necessitating the need for pertinent prevention strategies at home. Asymptomatic cases can contribute significantly to Omicron transmission. By making asymptomatic people aware that they are already contagious, hence limiting their social contacts, it is possible to lower the transmission risk.