Background: Since the outbreak started in 2019, COVID-19 pandemic has a significant global impact. Due to the highly infective nature of SARS-CoV-2, the COVID-19 close contacts are at significant risk of contracting COVID-19. China’s experience in successfully controlling COVID-19 emphasized the importance of managing close contacts because this strategy helps to limit potential infection sources, prevent the unconscious spread of COVID-19 and thus control this pandemic. As a result, to understand and consider the management of close contacts may be beneficial to other countries. However, managing close contacts is challenging owing to the huge number of close contacts and a lack of appropriate management tools and literature references. Methods: A new system called the COVID-19 Close Contact Information Management System was developed. Here we introduced the design, use, improvement and achievements of this system. Results: This system was designed from the standpoint of the Centers for Disease Control and Prevention in charge of managing close contacts. Two main functions and eight modules/themes were ultimately formed after two development stages. The system introduces what information need to be collected in the close contact management. Since the system allows information flow across cities, the geographical distance and administrative regional boundaries are no longer obstacles for managing close contacts, which promotes the management of each close contact. Moreover, when this system is used in conjunction with other data tools, it provides data assistance for understanding the COVID-19 characteristics and formulating targeted COVID-19 control policies. To date, the system has been widely used in Guangdong Province for over 1 year and has recorded tens of thousands of pieces of data. There is sufficient practical experience to suggest that the system is capable of meeting the professional work requirements for close contact management. Conclusions: This system provides a new way to manage close contacts and restrict the spread of COVID-19 by combining information technology with disease prevention and control strategies in the realm of public health. We hope that this system will serve as an example and guide for those anticipating similar work in other countries in response to current and future public health incidents.

Smoking-related metal exposure involves complex mixtures, yet its combined effects on gut microbiota and colorectal polyp progression remain unclear. We constructed a multi-metal disruption index integrating urinary arsenic, cadmium, and zinc concentrations that differed significantly between smokers and non-smokers in 196 colorectal polyp patients in 2023-2024 and examined its associations with gut microbiota and colorectal polyp progression. The index showed dose-dependent increases in detection rates of Limosilactobacillus, Methylovirgula and Peptoclostridium, with the most robust association observed for Limosilactobacillus after adjusting for covariates (OR = 3.39, 95%CI: 1.49–7.76, p = 0.004). Its detection rate was broadly negatively associated with the predicted abundance of pathways such as metabolism and organismal systems. In stratified analyses, the number of pathways with decreased predicted abundance among Limosilactobacillus-positive samples increased significantly as index levels rose (low: 0/27; medium: 15/27; high: 19/27), with 10 pathways significant at both medium and high levels. This dose-dependent genus-level response was observed alongside population-level relative stability, as no significant associations were found between the index and colorectal polyp progression. This multi-Metal Index approach provides a practical framework for assessing the health effects of smoking-related multi-metal mixtures. The dose-dependent increase in Limosilactobacillus colonization, occurring together with the decreased predicted abundance of specific metabolic pathways, suggests a possible association with metal-related stress.