Acknowledgements and Funding
This work was supported by National Natural Science Foundation of China (No.81973990, No. 81900096, No.81770090) and Fundamental Research Funds for the Central Universities (No.2020kfyXGYJ030).
Ethical statement
Data collection and analysis of cases were determined by the National Health Commission of the People’s Republic of China to be part of a continuing public health outbreak investigation and were thus considered exempt from institutional review board approval.