Received: 25 February 2021
Accepted: 25 July 2021
First Online: 4 August 2021
: The Yunnan Provincial Center for Disease Control and Prevention ethics committee granted ethical approval (approval number: YNCDC-2021027) for the study and used de-identified surveillance data. Written informed consent was obtained from each adult patient or guardian (if the patient is younger than 18 years old) for the study.
: Not applicable.
: The authors report no conflicts of interest.