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Major outbreaks of influenza virus occurred in China in 2017-2018. To describe the pattern of influenza circulation and timing of seasonal epidemics, we analyzed data from influenza-like illness (ILI) specimens on surveillance wards of sentinel hospitals during 2014-2018. Among 1,890,084 ILI cases, 324,211 (17.2%) tested positive for influenza. Influenza A virus (particularly A/H3N2), which circulates annually, was detected in 62% of cases, compared with influenza B virus in 38% of cases. The detection rate of A/H1N1, A/H3N2, B/Victoria, and B/Yamagata viruses were 3.56%, 7.07%, 2.08%, and 3.45%, respectively. Influenza prevalence was generally stable over the four years analyzed, but obvious outbreaks occurred in 2015-2016 (17.28%) and 2017-2018 (22.67%), with B/Victoria and B/Yamagata contributing to these outbreaks, respectively. In the south, a characteristic peak in infections was detected in the summer (week 23-38), which was not detected in the north. Influenza B was found high frequency in school-age children (5-14 years) with 4.78% of B/Victoria and 6.76% of B/Yamagata. Therefore, the epidemiological characteristics of seasonal influenza were complex in China during 2014-2018, presenting distinctions in region, season, and susceptible population. These findings underline the importance of enhancing year-round influenza surveillance and provide a reference for the timing and variety of influenza vaccination., (© 2023. The Author(s).)

Objective: To compare the accuracy of influenza-like illness (ILI) surveillance by automatic computer analysis based on electronic medical records and by doctor's report. Methods: A total of 3 542 patients who presented to Yichang Central Hospital fever clinic, respiratory department or emergency department between April to October 2019 with an ICD-10 code for acute respiratory illness (J00-J22) and complete electronic medical information of ILI related syndromes were drawn as the study sample. Taking the classification of the study sample according to the ILI case definition by influenza surveillance professionals as the gold standard, draw the receiver operating characteristic (ROC) curve and calculate sensitivity, specificity, diagnostic consistency to compared the accuracy of ILI surveillance by automatic computer analysis and by doctor's report. Results: Median age of 3 542 cases was 30 (24, 38) years old; 1 179 cases (33.29%) compliance with the case definition, ILI reported by doctors was 1 306 cases (36.87%), and computer automatic identification ILI were 1 150 cases (32.47%); 1 391 (39.27%) cases were men. The results of automatic computer analysis and doctor report consistency of kappa values with gold standard judgment were 0.97 and 0.66 respectively; area under the ROC curve was 0.98 and 0.84, respectively. And the sensitivity and specificity of automatic computer analysis were higher than that of doctor's report (all P values were <0.001), the sensitivity was 96.95% and 82.27%, and the specificity was 99.70% and 85.78%, respectively. Conclusion: The automatic computer analysis based on electronic medical records can identified ILI cases with good sensitivity and specificity in ILI case surveillance.

Objectives: To understand the status of studies about influenza economic burden in mainland China and summarize their major results. Methods: The words of influenza, flu, cost, economic, burden, effectiveness, benefit, utility, China, and Chinese, were used as search keywords. Journal papers published during 2000-2018 were searched from Chinese electronic databases (CNKI and Wanfang) and English electronic databases (PubMed, Web of science, EconLit and Cochrane Library). The language of literature was restricted to Chinese and English. A total of 23 effective documents were included, and the descriptive characteristics, research indexes and methods included in the literature were analyzed. The monetary unit used in this review is Chinese Yuan (CNY). Results: The 23 study sites were mainly in the relatively developed and populous regions. The total cost per capita of laboratory-confirmed influenza,of all age-group was reported in 6 literatures, and only 4 literatures reported it in out-patients (range: 768.0-999.9 CNY), Only one study reported this indicator in inpatients (9 832.0 CNY). One literature reported the total cost per capita of influenza-like illness,, which was 205.1 CNY. And one literature reported that the direct medical cost of inpatients per capita in children under 5 years of age was 6 072.0 CNY while two literature reported this index for the elderly over 60 years of age, ranging from 14 250.0 to 19 349.1 CNY. Four articles reported the economic burden of influenza in urban and rural areas, one of which showed that the related expenses of urban influenza inpatients accounted for 31% of the average annual income, while which for the rural flow was 113%. Conclusion: The average economic burden of lab-confirmed influenza case is higher than that of influenza-like illness, and there are differences in outpatient indirect expenses and inpatients direct medical expenses. The direct medical burden for the hospitalized 60-years-and-beyond influenza case group is heavier thar other age group. By region, the influenza associated individual economic burden in rural area is higher than that of urban area..

Objective: To systematically review the mortality burden study of influenza in mainland China. Method: "influenza", "flu", "H1N1", "pandemic", "mortality", "death", "fatality", "burden", "China" and "Chinese" were used as keywords, and a systematic literature search was conducted to identify articles in three English databases (PubMed, Web of Science and Embase) and three Chinese database (CNKI, WanFang and VIP) during 1990-2018 (excluding Hong Kong, Macao and Taiwan). The language of literature was restricted to Chinese and English. The inclusion criteria were human-oriented researches with method based on population, and research indexes included mortality and excess mortality. The exclusion criteria were non-primary research materials, predictive research and research on the burden of avian influenza related deaths. A total of 17 literatures were included, and the basic information to descriptive characteristics, methodology of modeling and the corresponding results were extracted. Results: All the 17 studies adopted indirect statistical models, with 14 of which adopted the regression model, and all the research index was excess mortality. All causes (16 studies), respiratory and circulatory diseases (14 studies) and pneumonia and influenza (10 studies) were the main causes of death associated with influenza. Influenza associated mortality burden in the elderly was higher, with the lowest excess mortality rates of all causes, respiratory and circulatory diseases, pneumonia and influenza being 49.57, 30.80 and 0.69 per 100 000 people, and the highest rates being 228.16, 170.20 and 30.35 per 100 000 people, respectively. In the non-elderly, the corresponding lowest rates were -0.27, -0.08 and 0.04 per 100 000 people respectively, and the highest rates were 3.63, 2.6 and 0.91 per 100 000 people, respectively. The influenza-related excess mortality was higher in the north, with a minimum of 7.8 per 100 000 and a maximum of 18.0 per 100 000, and slightly lower in the south, with a minimum of 6.11 per 100 000 and a maximum of 18.7 per 100 000. There were also differences in deaths caused by different influenza virus subtypes, with influenza A(H3N2) and influenza B virus possibly posing a heavier mortality burden. Conclusions: Studies on influenza mortality burden is mainly based on indirect model and urban level in China. The mortality burden of influenza in the elderly, the northern and subtype A(H3N2) and B were more severe.