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Article History

Received: 25 May 2026

Accepted: 20 July 2026

First Online: 28 July 2026

Declarations

Ethics approval and consent to participate: This study was a retrospective epidemiological analysis based entirely on existing surveillance records from the China Information System for Disease Control and Prevention (CISDCP), the national mandatory reporting system for notifiable infectious diseases. The data used were fully anonymized at the source, containing no personally identifiable information. No human experiments or human tissues were collected. According to the Measures for Ethical Review of Life Sciences and Medical Research Involving Human Subjects (Jointly issued by the National Health Commission of China and other ministries, 2023), research activities that solely involve analysis of anonymized, routinely collected public health surveillance data are exempt from formal ethical review board approval. The need for individual informed consent was waived because the study involved no direct contact with participants, which is consistent with the provisions of the Declaration of Helsinki for research using pre-existing, anonymized data. All methods were performed in accordance with relevant guidelines and regulations, including the Declaration of Helsinki. This activity was conducted as part of the routine disease control mandate of the Chinese Center for Disease Control and Prevention and was determined to be exempt from institutional review board approval according to national regulations (the Measures for Ethical Review of Life Sciences and Medical Research Involving Human Subjects), without requiring a specific ethics committee reference number.

Consent for publication: Not applicable.

Competing interests: The authors declare no competing interests.