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ObjectiveTo investigate the epidemiological trends of influenza in Yiwu City, Zhejiang Province from 2017 to 2022, and to provide references for local adjustments to influenza prevention and control strategies.MethodsReal-time fluorescence quantitative PCR was used to detect and type influenza viruses in nasal and pharyngeal swab specimens of the patients with influenza-like illness (ILI). The results were statistically analyzed.ResultsFrom 2017 to 2022, a total of 106 661 ILI cases were reported in Yiwu City, with annual reported cases of 31 273, 33 522, 20 090, 9 965, 3 202, and 8 609, respectively. The majority of ILI cases were in the age group of ≤14 years, accounting for 89.16%. A total of 6 893 specimens were collected and tested, of which 945 were tested positive for influenza virus nucleic acid, with an overall positivity rate of 13.71%. The dominant subtypes were H3N2 and B⁃Victoria, accounting for 40.63% (384/945) and 35.03% (331/945) respectively. The highest positivity rate was in 2019, at 25.19% (265/1 052). The positivity rates significantly decreased in 2020 and 2021, to 5.74% (66/1 149) and 5.77% (75/1 300), respectively. The rate increased in 2022 to 13.85% (180/1 300). The highest proportion of A/H3N2 positivity was in 2017, at 69.14% (168/243). The highest proportion of A/H1N1 positivity was in 2018,at 50.86%(59/116). The highest proportion of B/Victoria positivity was in 2021, at 100.00% (75/75). The highest proportion of B/Yamagata positivity was in 2018, at 5.17% (6/116).ConclusionInfluenza in Yiwu City exhibits obvious seasonal patterns, with two peaks in winter-spring and summer. Dominant strains such as A/H3N2, B/Victoria, and A/H1N1 alternate or co-circulate. During the COVID-19 pandemic, seasonal influenza significantly decreased, and a series of prevention and control measures had a positive effect on influenza prevention and control.

Objective To analyze the results of influenza sentinel surveillance in Sichuan Province from 2020 to 2022, to pro- vide basis for influenza prevention and control in Sichuan. Methods The surveillance data of influenza-like illness (ILI) re- ported by 30 national influenza surveillance sentinel hospitals in Sichuan Province were collected through China Influenza Surveillance Information System, and the results of influenza sentinel surveillance in Sichuan Province from 2020 to 2022 were analyzed retrospectively by descriptive epidemiological methods. Results From 2020 to 2022, there was a correlation be- tween the proportion of ILI to the total number of outpatient and emergency surveillance cases (ILI%) and the detection rate of influenza in ILI samples (r=0.626, P < 0.001). From 2020 to 2022, a total of 103 544 influenza samples were collected and tested in Sichuan Province, of which 8 798 were tested positive, with a positive rate of 8.50%. In 2020, the epidemic level of influenza in Sichuan Province was low, and the epidemic peak was in January, which was co-epidemic of subtype A (H3N2) and strain B (Victoria). In 2021, the epidemic peak was in autumn and winter, and the dominant strain was strain B (Victoria). In 2022, there was an obvious summer epidemic peak in Sichuan Province, and the dominant strain was subtype A (H3N2). There were significant differences in the positive rate of ILI among different years, age groups, and cities and states (P<0.001). Conclusion Influenza B (Yamagata) was not detected in Sichuan Province from 2020 to 2022, and the main epidemic strain were A(H3N2) and B(Victoria). The epidemic strains in Sichuan Province displayed decreased epidemic levels at the end of 2020 and 2022, which may be attributed to the COVID-19 preventive and control efforts and the occurrence of viral interference. It is necessary to continue influenza surveillance and strengthen the prevention and control of influenza in children and students. [ABSTRACT FROM AUTHOR]

ObjectiveTo describe epidemiological characteristics of influenza-like illness (ILI) cases reported during 2021 – 22 by sentinel hospitals in Xiamen city, Fujian province for providing evidence to influenza prevention and control. Methods Demographic and medical information for 6 018 ILI cases reported by sentinel hospitals in Xiamen city from August 2021 to July 2022 were collected from National Influenza Surveillance Information System. Epidemiological and pathogenetic characteristics of the ILL cases were analyzed statistically. ResultsOf all the registered ILI cases, 51.99% (3 129) were male and 48.01% (2 889) were female; 49.72% (2 992) were at ages of 3 – 6 years; and 52.64% (3168) were reported during June 2022. For 2 794 pharyngeal swab specimens randomly collected from 46.43% of all cases, 1 683 were positive for influenza virus nucleic acid, with a detection rate of 60.24%. Single-strain infection were detected among most (1 536, 91.27% ) of the cases positive for influenza virus and the ratios of the isolated strains for the single infections were 57.75% for influenza A H3N2, 31.91% for influenza B Victoria lineage, and 1.60% for influenza A H1N1, respectively. The most detected co-infections were caused by influenza B Victoria lineage combined with human metapneumovirus infection, which was identified in 32 cases, accounting for 1.90% of the nucleic acid-positive ILI cases. ConclusionAccording to hospital-based sentinel surveillance, the ILI incidence showed a mono-peak in summer season and mainly caused by influenza A H3N2 and 3 – 6 years children were more susceptible to the influenza-like infection during 2021 – 22 in Xiamen city.

ObjectiveTo analyze the surveillance results of influenza-like illness （ILI） cases in a sentinel hospital in Nantong from 2014 to 2021 and to understand the seasonal and etiological characteristics of influenza.MethodsThe routine ILI case information in a sentinel hospital in Nantong from 2014 to 2021 was collected from China Influenza Surveillance Information system， and the surveillance results were described and analyzed.ResultsA total of 64 110 ILI cases were reported in the hospital from 2014 to 2021， and accounted for 3.93% of outpatient and emergency visits. ILI is mainly concentrated in children under 15 years old， accounting for 55.39% of the total ILI cases. ILI% roughly showed two epidemic peaks in spring and winter. A total of 8 639 nasopharyngeal swab samples of ILI cases were collected during 2014‒2021， of which 838 were influenza positive， with an average positive rate of 10.01% （3.27%‒16.75%）. The epidemic strains varied from year to year and in different age groups. In 2014 and 2015， H3N2 influenza was the epidemic strain； in 2016 and 2017， H3N2 influenza and B-Victoria influenza were the co-epidemic strains； in 2018， H1N1 influenza was the epidemic strain； and in 2019‒2021， B Victoria influenza was the epidemic strain. The epidemic strain in 0‒4 years old， 15‒24 years old， 25‒59 years old and >60 years old was H3N2， and the epidemic strain in 5‒14 years old was B Victoria. There was a significant difference in the positive rate between different gender groups （χ2=7.364， P=0.006）.ConclusionInfluenza often occurs in winter and spring in a sentinel hospital in Nantong. Influenza subtypes are prevalent alternately in different age groups and different years. We need to closely monitor the etiology of influenza virus in Nantong to provide a basis for influenza prevention and control.

Objective To evaluate the influence of coronavirus disease 2019 (COVID-19) prevention and control measures on the transmission and epidemic of influenza in Chongqing, so as to provide references for formulating targeted influenza prevention and control strategies. Methods The influenza surveillance data, during the year 2018 to 2020, were collected through the "China Influenza Surveillance Information System", and the seasonal characteristics of influenza epidemic were analyzed. The percentage of influenza like cases (ILI%) and influenza virus positive rate between 2020 and 2018-2019 were compared, so as to evaluate the impact of COVID-19 prevention and control measures on influenza epidemic characteristics. Results The annual proportions of ILI cases in Chongqing were respectively 3.53%, 2.23% and 1.2% from 2018 to 2020, while the positive rates of influenza virus were respectively 13.97%, 23.81% and 2.65%. The distribution trend of ILI% from 2018 to 2019 fluctuated were similar, but it continued to drop and remain at a low level since February 2020. The positive rate of influenza virus showed an epidemic peak from December to March in 2018-2019, also peaked from November 2019 to January 2020, but decreased to 0 in March. ILI% was positively correlated with the positive rate of influenza virus (r= 0.404 8, P<0.05). In 2020, compared with the same period of 2018-2019, the growth rate of ILI% was -66.09% and -46.32%, respectively. The positive rate of influenza virus in 2020 decreased by 81.03% and 88.87% compared with the same period of 2018-2019, respectively. The growth rates of influenza virus positive rate in January 2020 were decreased with a small rate of about 39.87%, and with a significantly decline of more than 93.65% from February. No influenza epidemic was found after March. Conclusions Since COVID-19 prevention and control measures were implemented in January 2020 in Chongqing, the ILI% and the positive rate of influenza virus in sentinel hospitals decreased significantly. In the season of high incidence of respiratory infectious diseases, personal protection and other measures can effectively reduce influenza virus infection. [ABSTRACT FROM AUTHOR]

ObjectiveTo perform the analysis of influenza surveillance in Dehong from 2016 to 2020 and determine the epidemic situation of influenza and prevalent virus strains， so as to provide evidence for local influenza prevention and control.MethodsThe influenza surveillance data in Dehong Prefecture was collected from January 2016 to December 2020. Statistical analysis was conducted by descriptive epidemiological methods.ResultsA total of 4 146 samples from influenza-like illness cases were examined. The 502 specimens tested positive for influenza virus， including 311 cases with influenza A virus and 136 cases with influenza B virus， resulting in a positive rate of 12.11%. The positive rate was the highest in 2017， followed by 2019， and the lowest in 2020 （P < 0.05）. It peaked in winter and fall. Furthermore， it was the lowest among children aged 0‒4 years and the highest among adults aged 25‒59 （P < 0.001）. In addition， positive rate did not differ significantly by gender（P>0.05）ConclusionThe positive rate of influenza has decreased in Dehong since January 2020. The influenza epidemic is seasonal， mainly in fall and winter， except 2020. Influenza A virus is predominant， compared to alternating influenza B virus.

Objective To analyze prevalence characteristics and variation trend of influenza in Guizhou province during 2011– 2021 and to provide evidences for influenza prevention and control. Methods Throat swab specimens were collected from influenza-like illness (ILI) cases at fever/internal medicine and pediatric clinics of 13 national influenza sentinel surveillance hospitals in Guizhou province during 2011 – 2021 and detected with real-time reverse transcription-polymerase chain reaction (RT-PCR). Statistical analysis was conducted on the basis of annual influenza seasons. ResultsOf the 135 537 specimens detected during the 10-year period, 16.73% (22 676) were positive for influenza virus nucleic acid. Among the positive specimens, the detection rate was the highest (34.3%) for subtype of H3N2 and the lowest (13.69%) for subtype of BY. Various viral subtypes were prevalent alternately during the period. Two prevalence peaks of influenza virus infection in winter-spring season and in summer season were observed, with slightly more infectious cases among females than among males and more cases among the people aged 5 – 24 years. There was a subtype-specific difference in the susceptibility of influenza virus in various populations and there was a significant difference in annual positive rate for the specimens detected. ConclusionDuring 2011 – 2021 in Guizhou province, influenza was prevalence periodically with alternative prevalent viral subtypes; more influenza infections occurred in winter-spring and in summer seasons, especially among young people. The results suggest that surveillance and analysis on viral strain variation timely should be strengthened.

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Objectives: Taiwan had its longest recorded cold wave during the 2016 Chinese New Year holiday; a surge in influenza cases followed. To assess the effect of a cold wave on influenza activity, we used a time series model to analyze the relationship between low ambient temperatures and influenza-related emergency visits. Methods: We obtained weekly data on the proportion of influenza-like illnesses (ILIs) among emergency room visits in Taipei from January 2007 to December 2016. Data were from the Real-time Outbreak and Disease Surveillance of the Taiwan Centers for Disease Control. Ambient temperature data were from the Taiwan Central Weather Bureau. We used an autoregressive integrated moving average (ARIMA) model to analyze the association between low temperatures and ILIs. The validity of predictive models was tested against January 2017 to December 2017 data as external validation. Results: The time series of ILI-related emergency visits in Taipei was consistent with the ARIMA (1, 1) model at an autoregression coefficient of 0.92 (p < 0.001). ARIMA analysis indicated that the lowest temperature in the previous week (coefficient: -0.07, p = 0.01) and the number of holiday days in the week (coefficient: 0.2, p < 0.001) were significant predictors of the proportion of ILI-related emergency visits. External validation demonstrated that the time series model with temperature and holiday covariates accurately predicted the timing of the ILI surge in the 2017 winter vacation, with an R2 of 85% for the overall fit in 2017. Conclusions: Cold waves are a predictor of increased ILI-related emergency visits. Thus, influenza preparedness measures should incorporate ambient temperature forecasts. [ABSTRACT FROM AUTHOR]

Copyright of China Tropical Medicine is the property of China Tropical Medicine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Tropical Medicine is the property of China Tropical Medicine Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective To analyze the pathogen spectrum of influenza virus-negative nasopharyngeal swabs from 150 influenza-like illness (ILI) cases during flu epidemic season. Methods Totally 150 influenza virus-negative nasopharyn­geal swabs specimens were selected randomly for the respiratory syncytial virus (RSV) , adenovirus (AdV) , human rhino- virus (HRV) and coronavirus (CoV) detection by using real-time PCR. Results Of 150 influenza-like cases，44 cases were virus positive with the positive rate of 29. 33% (44/150)，including 22 cases of RSV infection (14. 67% )，9 cases of AdV infection (6. 00% )，5 cases of HRV infection (3.33% ) and 5 cases of CoV infection (3.33% ) including 1 case of COV-229E (0. 67% ) , 1 case of COV-NL63 (0. 67% ) and 3 cases of COV-OC43(2. 00% ) . There were 3 cases of co­infection (2. 00% )，which were RSVB co-infected with COV-OC43，AdV and HRV，respectively. The pathogen spectrum analysis showed that RSVA accounted for 6.81% of the total positive samples，RSVB accounted for 43. 18%，AdV accoun­ted for 20.45%，HRV accounted for 11. 36%， CoV accounted for 11.36%，and co-infection accounted for 6. 81%. In addition，the positive rate was 32.10% (26/81) in males and 26. 09% (18/69) in females, and no significant difference was found between males and females ( P > 0. 05 ). The positive rate was 41. 07% (23/56) in the children under four years old，36.37% (8/22) in the age of 4-18，16.98% (9/53) in the age of 19-59，and 21.05% (4/19) in the old people above 60 years old，with significant difference ( all P <0.05 ). RSV，AdV and HRV were the main viruses infected in the children under 4 years old, and no HRV was detected in the old people above 60 years old. Conclusion RSV， AdV, HRV，and CoV could be detected in the influenza-like cases，and the children under 4 years old，are more mainly infected with RSV，AdV，and HRV. [ABSTRACT FROM AUTHOR]

Shanghai Municipal Center for Disease Control and Prevention has implemented an active comprehensive surveillance project of acute respiratory infections in adults in Shanghai, including influenza like illness (ILI) and severe acute respiratory infection (SARI). By testing and identifying a variety of respiratory pathogens, it was found that influenza viruses were the main pathogens in 172 ILI cases in 2019. The positive rates of influenza A (H1N1) pdm09 virus, influenza A (H3N2) virus and influenza B virus Victoria lineage were 30.81%, 14.53% and 30.55%, respectively. The positive detection of influenza A (H1N1) pdm09 virus peaked in the first quarter. The positive rate of enterovirus/human rhinovirus was 6.40%, with a positive detection peak in the third quarter, while the positive rate of adenovirus was 4.65% with a positive detection peak in the second quarter of the year. Two human coronavirus (HCoV)-OC43 positive samples, 1 HCoV-HKU1 positive sample and 1 HCoV-NL63 positive sample were detected, respectively, and no HCoV-229E positive sample was detected. The detection rate of Staphylococcus aureus was 17.44%, and the detection rate of Klebsiella pneumoniae was 9.88%. Influenza viruses were also the main pathogens in 1 447 SARI cases. The positive rates of influenza A (H1N1) pdm09 virus, influenza A (H3N2) virus and influenza B virus Victoria lineage were 5.46%, 1.73% and 0.30%, respectively. The positive detection of influenza A (H1N1) pdm09 virus (17.50%) peaked in the first quarter. The total positive detection rate of enterovirus/human rhinovirus was 2.97%, the positive detection peaked in the first quarter. The positive rate of Mycoplasma pneumoniae was 3.25% and the positive rate of Legionella was 1.04%. 5 HCoV-229E positive samples, 10 HCoV-OC43 positive samples, 7 HCoV-HKU1 positive samples and 6 HCoV-NL63 positive samples were detected. Eight strains of Staphylococcus aureus , 4 strains of Pseudomonas aeruginosa and 3 strains of Klebsiella pneumoniae were detected after cultures. By implementing the active surveillance, we not only detected a case of human infection with avian influenza A(H7N9) virus in time, but also preliminary understood the pathogenic spectrum characteristics and seasonality of ILI and SARI in Shanghai. In recent years, the surveillance methods have been continuously improved and the number of sentinel hospitals has increased gradually. In particular, for the response to COVID-19, the Surveillance Information Reporting System of Acute Respiratory Infection based on HIS system has been promoted to cover the whole city, which might lay a foundation for the active surveillance and early warning of emerging infectious diseases in the future.

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.

Objective: To analyze the reasons for the fluctuations in the percentage of outpatient or emergency visits for influenza-like illness (ILI) during the Spring Festival and National Day in 2014-2018 surveillance season. Methods: ILI surveillance data was collected during the period of Spring Festival and National Day in mainland China, and downloaded from Chinese Influenza Surveillance Information System, during the 2014-2018 surveillance season. Results: There was no significant difference noticed in the number of ILI reports in the festival week with weeks before or after in both the southern and northern provinces. The number of outpatient visits was much less than that of the week before and after, but the number of emergency visits was statistically significantly increased. Conclusion: In the holiday peak of ILI%, the major causes was the impact of holiday-off at sentinel hospitals, resulting in a large reduction in the number of outpatient visits in the consulting room during the festivals.