Two Peaks of Seasonal Influenza Epidemics — China, 2023

Yiran Xie¹; Shuxia Lin¹; Xiaoxu Zeng¹; Jing Tang¹; Yanhui Cheng¹; Weijuan Huang¹; Jiandong Li¹; Dayan Wang^1#

1.National Key Laboratory of Intelligent Tracking and Forecasting for Infectious Disease, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.

#Correspondence author: Dayan Wang, wangdayan@ivdc.chinacdc.cn.

This research reveals significant differences from historical patterns due to the impacts of COVID-19. According to the Chinese National Influenza Surveillance Network, influenza activity exhibited two distinct epidemic waves: an initial peak dominated by the A(H1N1)pdm09 subtype between February and April, the second peak driven by A(H3N2) and B/Victoria viruses from October to December. The first wave began two months later than usual, resulting from reduced population immunity and increased mobility post-COVID-19 restrictions. The second wave, starting earlier than typical winter peaks, was influenced by school re-openings and cooler weather. A summer epidemic, typically seen in the southern regions, was absent this year. These findings suggest a shift in influenza seasonality patterns due to COVID-19 outbreak is gradually returning to its usual seasonal and intensity patterns, necessitating continuous enhancement of influenza surveillance and the influenza surveillance network, to adapt to evolving epidemiological landscapes.

季节性流感呈现两个流行高峰 — 中国，2023年

谢怡然¹；林淑霞¹；曾晓旭¹；唐静¹; 成艳辉¹; 黄维娟¹; 李建东¹; 王大燕^1#

1传染病溯源预警与智能决策全国重点实验室，病毒病预防控制所，中国疾病预防控制中心，北京，中国。

#通讯作者：王大燕，wangdayan@ivdc.chinacdc.cn。

研究显示，受COVID-19 的影响，2023年我国流感活动呈现与既往显著不同的流行特征。根据全国流感监测网络的数据，流感活动呈现出两个明显的流行高峰：2 月至 4 月期间以A(H1N1)pdm09亚型为主的首个高峰，随后在10月至12月期间由A(H3N2) 和B/Victoria系病毒导致的第二个高峰。第一波疫情比既往晚了两个月开始，与 COVID-19 后人群流动性增加以及人群对A(H1N1)pdm09）流感病毒的免疫力下降有关（作者注：新冠大流行期间我国A(H1N1)pdm09）流感病毒未流行）。第二波疫情比既往典型的冬季高峰期更早开始。值得注意的是，2023年没有出现南方省份典型的夏季流感流行。本研究表明流感的季节性模式曾受COVID-19疫情影响发生了变化，但已恢复到通常的季节性特征和强度模式，需要持续加强流感监测，强化流感监测网络建设，以适应不断变化的流行病学形势。

For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.069

Rodent Ecology and Etiological Investigation in China: Results from Vector Biology Surveillance — Shandong Province, China, 2012–2022

Qintong Sun¹; Yan Liu¹; Yingnan Han¹; Wenjie Liu¹; Xinyue Cao¹; Binghui Li²; Xuejun Wang^1# 

1.  Institute of Disinfection & Vector Borne Disease Control, Shandong Center for Disease Control and Prevention/ Shandong Academy of Preventive Medicine, Jinan City, Shandong Province, China;

2. Institute of Disinfection and Vector Control, Qingdao Center for Disease Control and Prevention/Qingdao Institute of Preventive Medicine, Qingdao City, Shandong Province, China.

# Corresponding author: Xuejun Wang, bmfzs@126.com.

Rodents are the hosts of a wide range of zoonotic disease pathogens, which threaten human health. However, there is a lack of comprehensive investigation of rodent ecology and etiology in Shandong. Thus, this study aimed to analyze the rodent ecology and the relevant pathogens infection in Shandong Province, China. A collection of rodent survey data from 2012–2022 in Shandong Province was used, and rodent captured in 2020–2022 were identified by species and tested for pathogens. From 2012–2022, 4,145 Rodents were captured. The average rodent capture rate was 0.70%. High capture rates of rodents were rural residential areas and other (farmland, forestland) habitats. Rattus norvegicus (R. norvegicus) as the dominant species, followed by Mus musculus (M.musculus). The regions with high capture rates of R. norvegicus were mainly distributed in Dongying (0.82%) and Heze (0.63%). M. musculus was higher in Dongying (0.81%), Weihai (0.56%). The months with high rodent capture rates are mainly March–September. The positive detection rates of rodents Hantavirus (HV), Leptospira interrogans (L. interrogans), Rickettsia typhi (R. typhi), Anaplasma phagocytophilum (A. phagocytophilum), and Francisella tularensis (F. tularensis) were 2.58%, 1.10%, 0.94%, 0.16%, and 0.19%, respectively. The capture rate of rodents in the human habitation environment has been on a downward trend in Shandong Province, and the species is dominated by R. norvegicus and M.musculus. There was a certain seasonal trend and a risk of infection by HV, L. interrogans and R. typhi in rodents. Strengthen the work of rodents’ surveillance, maintain a low capture rate of the host animals could be pivotal for prevent and control relevant rodent-borne diseases in high-risk areas.

媒介鼠类生态学与病原学监测结果分析 — 山东省，中国，2012–2022年

孙钦同¹；刘  言¹；韩英男¹；刘文杰¹；曹馨月¹；李炳辉²；王学军^1#

1.山东省疾病预防控制中心消毒与病媒生物防制所/山东省预防医学科学院，济南市，山东省，中国；

2.青岛市疾病预防控制中心消毒与病媒生物防制所/青岛市预防医学研究院, 青岛，山东，中国。

#通讯作者：王学军，bmfzs@126.com。

鼠类是多种人畜共患疾病病原体的宿主，威胁着人类健康。然而，山东省内缺乏对鼠类生态学和病因学方面的全面调查。本文旨在分析山东省的鼠类生态学及其相关病原体感染情况。研究收集了山东省2012–2022年的鼠类生态学调查数据，并对2020–2022年捕获的鼠类进行了种类鉴定和病原体检测。从 2012 年到 2022 年，捕获了 4,145 只鼠类。平均鼠类捕获率为0.70%。农村居民区和其他（农田、林地）栖息地的鼠类捕获率较高。褐家鼠（R. norvegicus）为优势种，其次是小家鼠（M.musculus）。山东省褐家鼠捕获率较高的地区主要分布在东营市（0.82%）和菏泽市（0.63%）。而东营市（0.81%）、威海市（0.56%）的小家鼠捕获率较高。山东省鼠类捕获率高的月份主要是 3月–9月。鼠体内汉坦病毒（HV）、钩端螺旋体（L. interrogans）、伤寒立克次体（R. typhi）、嗜吞噬细胞无形体（A. phagocytophilum）、土拉弗朗西斯菌（F. tularensis）的阳性检出率分别为2.58%、1.10%、0.94%、0.16%、0.19%。通过研究，山东省人居环境中鼠类的捕获率呈下降趋势，以褐家鼠和小家鼠为主。年内鼠类捕获率有一定的季节变化趋势。鼠体内检出 HV、L. interrogans 和 R. typhi阳性率较高。高风险区应进一步加强鼠类监测，进一步降低鼠类捕获率，可有效预防和控制鼠传疾病。

For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.193

Comparison of Three Influenza Surveillance Data Sources for Timely Detection of Epidemic Onset — Chengdu City, Sichuan Province and Beijing Municipality, China, 2017–2023

Mingyue Pan¹; Ying Shen^1,2;  Yao Wang³; Lu Long³，Xunbo Du³, Ying Sun^1,2; Daitao Zhang^1,2; Hui Yao¹; Yonghong Liu¹; Peng Yang^1,2; Quanyi Wang^1,2; Xiaoli Wang^1,2#; Liang Wang^3#

1 Beijing Center for Disease Prevention and Control, Beijing, China;

2 Beijing Research Center for Respiratory Infectious Diseases, Beijing, China;

3 Chengdu Center for Disease Control and Prevention, Chengdu, China.

^#Corresponding author: Xiaoli Wang, wangxiaoli198215@163.com; Liang Wang, 363686849@qq.com.

The influenza-like illness (ILI) surveillance system in China is a vital component of syndromic surveillance and has historically been pivotal in early warning of influenza epidemics. However, its efficacy is challenged because it can hardly reflect the activity of influenza virus when multiple pathogens are circulating. China also has two other influenza surveillance systems: The nationwide Notifiable Infectious Diseases Reporting Information System (NIDRIS) and the Virological Surveillance System. The NIDRIS is characterized by nationwide coverage, mandatory reporting, high specificity, and real-time reporting. The Virological Surveillance System provides positivity rates of influenza, which is accurate in tracking virus activities but lags behind ILI and NIDRIS reports by a few days. This study aimed to compare the performance of the three surveillance datasets derived from the above systems to identify the best solution for timely onset detection of influenza epidemics. We used three datasets spanning the years 2017 to 2024 for early warning of influenza epidemics in Beijing and Chengdu, China. Specifically, the years 2021-2024 served as the test sets for our analysis. The first dataset was the daily number of reported influenza cases from NIDRIS. The second dataset consisted of the daily number of reported ILI cases from the ILI surveillance system (ILIs). The third dataset was generated by multiplying weekly ILI cases by the influenza positivity rate (PR), obtained from the Virological Surveillance System (ILIs*PR). Exponentially Weighted Moving Average (EWMA) and modified Cumulative Sum (modified-CUSUM) were used to evaluate the performance of the three datasets. The NIDRIS datasets demonstrated superior performance in early influenza detection, with an aggregated Youden Index of 0.905 in Beijing and 0.819 in Chengdu for 2021-2024 influenza seasons, outperforming both the ILIs (0.566 for Beijing and 0.490 for Chengdu) and the ILIs*PR (0.844 for Beijing and 0.740 for Chengdu). We suggest that public health practitioners use reported cases data in NIDRIS for more accurate timely onset detection of influenza epidemics, within the context of co-circulation of respiratory pathogens.

三种流感监测数据源用于流感流行早期预警的比较 — 四川省成都市和北京直辖市，中国，2017–2023 年

潘明月¹；沈莹^1，2；王瑶³；龙露³；杜训波³；孙瑛^1，2；张代涛^1，2；姚慧¹；刘永红¹；杨鹏^1，2；王全意^1，2；王小莉^1，2#；王亮^3#

1 北京市疾病预防控制中心，北京，中国

2 北京重大呼吸道传染病研究中心，北京，中国

3 成都市疾病预防控制中心，成都市，四川省，中国

#通讯作者：王小莉，wangxiaoli198215@163.com；王亮，363686849@qq.com。

流感样疾病（ILI）监测系统在流感流行的早期预警中至关重要。然而，当新冠、流感等多种病原体共同流行时，基于症状的流感样病例数很难反映流感病毒的活动情况。全国性法定传染病报告信息系统（大疫情网）和病原学监测系统也提供了潜在的可以用于流感早期预警的数据。其中大疫情网覆盖全国、强制报告且具特异性和实时性；病原学监测系统提供的病原学阳性率准确但缺乏及时性。本研究使用以上系统的数据建立了三组数据集，并评估其用于流感早期预警的效果。对北京和成都分别建立2017至2024年的三组流感流行预警数据集。第一组数据集是大疫情网报告的流感病例数；第二组数据集是ILI监测系统报告的流感样病例数（ILIs）；第三组数据集使用ILIs乘以病原学监测系统提供的流感阳性率生成（ILIs*PR）。使用指数加权移动平均（EWMA）和修正累积和（modified-CUSUM）评估三组数据集的流感早期预警效果。大疫情网报告的流感病例数在北京和成都的流感早期预警效果最佳，2021-2024年北京和成都的流感流行预警约登指数分别为0.905和0.819，优于ILIs（北京0.566，成都0.490）和ILIs*PR（北京0.844，成都0.740）。在多个呼吸道病原体共同流行的背景下，使用大疫情网报告的流感病例数建立预警模型，能够更准确及时地预警流感流行。。

For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.194

A Systematic Review of the Definition, Measurement, and Associated Factors of Pandemic Fatigue

Ruohan Chen^1,2*; Qi Tan^3*; Bowen Su²; Shuqi Wang⁴; Zhanwei Du^1,2# 

1 WHO Collaborating Center for Infectious Disease Epidemiology and Control, School of Public Health, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China;

2 Laboratory of Data Discovery for Health Limited, Hong Kong Science Park, Hong Kong Special Administrative Region, China;

3 Nanjing Tech University, Nanjing City, Jiangsu Province, China;

4 School of Cybersecurity, Northwestern Polytechnical University, Xi'an City, Shaanxi Province, China.

* Joint first authors.

^# Corresponding author: Zhanwei Du, zwdu@hku.hk.

The rapid emergence and widespread transmission of SARS-CoV-2 have prompted governments worldwide to enact policies and measures to manage the virus's spread. These interventions have substantially contributed to controlling disease transmission. However, they have also significantly disrupted daily life, leading to increased public fatigue and resistance to sustained control measures, a phenomenon known as pandemic fatigue. To develop a comprehensive understanding of pandemic fatigue, this review systematically explores the concept and identifies quantitative indicators for measuring it. We reviewed studies on pandemic fatigue across various countries, summarized the contributing factors, and analyzed its impact on personal protective behaviors. Our findings indicate that the enforcement of health measures significantly influences the onset of pandemic fatigue, while individual perceptions of risk can negatively affect personal protective behaviors, creating a feedback loop with increasing fatigue. These results underscore the importance of considering the current severity of the pandemic and individual decision-making processes in the implementation of interventions. Enhancing our understanding of pandemic fatigue is essential for developing effective policy responses in preparation for future potential epidemics.

对大流行性疲劳的定义、测量和相关因素的系统综述

陈若涵^1,2*；谭棋^3*；苏柏文²；王淑祺⁴；杜占玮^1,2# 

1 香港大学李嘉诚医学院公共卫生学院世卫传染病流行病学及控制合作中心，香港特别行政区，中国；

2 医卫大数据深析实验室，香港特别行政区，中国；

3 南京工业大学，南京市，江苏省，中国；

4 西北工业大学网络空间安全学院，西安市，陕西省，中国。

*共同第一作者。

#通讯作者：杜占玮，zwdu@hku.hk。

SARS-CoV-2的迅速出现和广泛传播促使世界各国政府制定政策和措施来控制病毒的传播。这些干预措施有助于控制疾病的传播。然而，这些干预措施也扰乱了人们的日常生活，导致公众对持续的控制措施产生了更多的疲劳和抵触情绪，这种现象被称为 “大流行疲劳”。为了全面了解大流行疲劳，本综述系统地探讨了这一概念，并确定了衡量这一概念的量化指标。我们回顾了各国关于大流行疲劳的研究，总结了造成疲劳的因素，并分析了疲劳对个人防护行为的影响。我们的研究结果表明，卫生措施的实施会对大流行性疲劳的发生产生重大影响，而个人对风险的感知会对个人防护行为产生负面影响，从而形成一个反馈循环，导致疲劳加剧。这些结果强调了在实施干预措施时考虑当前大流行病严重程度和个人决策过程的重要性。加强我们对大流行疲劳的了解对于制定有效的政策应对措施，为未来潜在的流行病做好准备至关重要。

For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.068

Socioeconomic Impact and Response Strategies to the Multifaceted Respiratory Illness Outbreak in Northern China: Beyond Influenza A and Mycoplasma Pneumoniae

Xi Wang^1*; Rongfeng Zhou^2*; Ting Li²; Shuai Du¹; Ayan Mao¹; Wuqi Qiu^1#; Hongzhou Lu^2#

1 Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China;

2 Department of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The Third People's Hospital of Shenzhen, Shenzhen City, Guangdong Province, China.

^* Joint first authors.

^# Corresponding Authors: Wuqi Qiu, qiu.wuqi@imicams.ac.cn; Hongzhou Lu, luhongzhou@fudan.edu.cn.

A recent study investigated the respiratory illness outbreak in Northern China, honing in on the surge of cases in Beijing from November to December 2023. The Beijing Center for Disease Prevention and Control reported a significant rise in influenza-like illnesses, with strains such as H3N2 and Mycoplasma pneumoniae predominating. The study highlighted the confluence of lifted COVID-19 restrictions, colder weather, and overlapping pathogen circulation as key drivers of this surge. Public health responses included expanding pediatric outpatient clinics, enhancing flu vaccine coverage, and stressing preventive measures. The study underscored the strain on healthcare resources and the necessity for robust surveillance systems and public health campaigns. Historical pandemics, like the Spanish Flu and COVID-19, provided valuable lessons in managing such outbreaks, emphasizing quarantine, vaccination, and public awareness as effective strategies. The study's recommendations for bolstering healthcare infrastructure, promoting public health education, and fostering international cooperation aim to inform future epidemic response strategies. This comprehensive analysis offers critical insights for public health professionals and policymakers in addressing the complex dynamics of respiratory illness outbreaks in urban environments.

中国北方涵盖甲型流感与肺炎支原体之外的多元呼吸道疾病暴发：社会经济影响及应对策略

王曦^1*；周荣锋^2*；李婷²；都率¹；毛阿燕¹；邱五七^1#；卢洪洲^2#

1. 中国医学科学院北京协和医学院，北京，中国；

2. 深圳市第三人民医院感染病临床医学研究中心，深圳市，广东省，中国。

*共同第一作者。

#通讯作者：邱五七，qiu.wuqi@imicams.ac.cn；卢洪洲，luhongzhou@fudan.edu.cn。

本研究旨在探讨华北地区，尤其是北京，在解除COVID-19限制措施后，呼吸道疾病暴发对社会经济和公共卫生的影响。研究重点分析了甲型流感（H3N2）和肺炎支原体病例激增对城市卫生系统和经济结构的冲击。研究采用了混合研究方法，包括对相关学术和政府文献的回顾、公共卫生数据的定量分析，以及应对策略的定性评估。研究结果表明，2023年下半年呼吸道疾病病例显著上升，卫生部门采取紧急措施，包括扩充医院容量和加强疾病监测。然而，资源短缺和公众对公共卫生的疲劳情绪成为应对过程中的主要挑战，影响了整体应对效果。尽管如此，及时的公共卫生响应措施在一定程度上控制了疫情，但也暴露出基础设施、监测体系以及政策框架方面的不足。基于研究结果，本文提出了若干建议，强调加强国际合作和完善应急预案的重要性。这些措施对于未来流行病的防控具有重要意义，能够为全球卫生安全提供更加有力的保障。

For more information: https://weekly.chinacdc.cn/en/article/doi/10.46234/ccdcw2024.196