Infectivity, susceptibility, and risk factors associated with SARS-CoV-2 transmission under intensive contact tracing in Hunan, China
Shixiong Hu, Wei Wang, Yan Wang, Maria Litvinova, Kaiwei Luo, Lingshuang Ren, Qianlai Sun, Xinghui Chen, Zeng Ge, Jing Li, Lu Liang, Zhihong Deng, Wen Zheng, Mei Li, Hao Yang, Jinxin Guo, Kai Wang, Xinhua Chen, Ziyan Liu, Yan Han, Huilin Shi, Zhiyuan Chen, Yonghong Zhou, Kaiyuan Sun, Alessandro Vespignani, Cécile Viboud, Lidong Gao, Marco Ajelli, Hongjie Yu
Abstract
Several mechanisms driving SARS-CoV-2 transmission remain unclear. Based on individual records of 1178 potential SARS-CoV-2 infectors and their 15,648 contacts in Hunan, China, we estimated key transmission parameters. The mean generation time was estimated to be 5.7 (median: 5.5, IQR: 4.5, 6.8) days, with infectiousness peaking 1.8 days before symptom onset, with 95% of transmission events occurring between 8.8 days before and 9.5 days after symptom onset. Most transmission events occurred during the pre-symptomatic phase (59.2%). SARS-CoV-2 susceptibility to infection increases with age, while transmissibility is not significantly different between age groups and between symptomatic and asymptomatic individuals. Contacts in households and exposure to first-generation cases are associated with higher odds of transmission. Our findings support the hypothesis that children can effectively transmit SARS-CoV-2 and highlight how pre-symptomatic and asymptomatic transmission can hinder control efforts.