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Application of moving epidemic method in early warning of influenza incidence intensity in winter-spring season in Ningbo city
DING Keqin, GU Shaohua, LAO Xuying,
, Available online  , doi: 10.11847/zgggws1140803
Abstract(129) HTML (43) PDF 1835KB(65)
  Objective  To explore the application of moving epidemic interval method (MEM) in early warning of influenza incidence intensity in winter-spring season in Ningbo city and to provide a reference for developing effective intervention measures.   Methods  Influenza surveillance data for the period of January 2013 – May 2022 were collected from 2 national influenza sentinel hospitals in Ningbo city, Zhejiang province and a part of the data on positive rate of influenza virus detection among the registered cases in winter-spring seasons from January 2013 to December 2019 were extracted to establish a MEM model. The constructed MEM model was adopted to analyzed the beginning, the end and incidence intensity seasonal influenza epidemic during 2019 – 2020 (40th week, 2019 – 20th week, 2020) in Ningbo city; the model analysis results were compared with actual situation of the epidemic.   Results  For the virus- positive cases in the city during the 2013 – 2022, the proportions of isolated viral strains were 24.59% for influenza A (H1N1), 37.03% for influenza A (H3N2), and 38.38% for influenza B (mainly Victoria and Yamagata strain), respectively. The established MEM model showed a better goodness-of-fit, with the parameter δ of 2.7, the sensitivity of 87.97%, the specificity of 87.68%, and the Yoden index of 0.76. Based on the fitting results of the established MEM model, the thresholds of virus-positive rate were 22.76% and 25.05% for identifying the onset and the end of the influenza epidemic and the thresholds were 43.18%, 63.22%, and 74.83% for indicating a moderate-, high-, extremely high-intensity of the influenza epidemic during 2019 – 2020 influenza season. With the established MEM threshold estimations, the trajectory of the influenza could described as following: pre-epidemic stage from 40th week to 48th week of 2019, onset/low- intensity stage from 49th week of 2019, moderate-intensity stage from 51th week if 2019 to third week of 2020, subsequent low-intensity stage from 4th week of 2020, late stage from 7th week of 2020, and the end of the epidemic by the 10th week of 2020. Compared to the seasonal epidemics between 2013 – 2019, the 2019 – 2020 winter spring influenza epidemic occurred one week earlier but ended three weeks sooner.   Conclusion   MEM model could be adopted effectively in early identification and intensity warning of seasonal influenza epidemic.
Effect of intervention on influenza vaccination during 2021 – 2022 influenza season among hospital professionals in a district of Shenzhen city
PENG Mingji, JIANG Shiqiang, CAI Yuwei,
, Available online  , doi: 10.11847/zgggws1140334
Abstract(183) HTML (39) PDF 475KB(74)
  Objective  To evaluate the effect of an intervention with a required non-mandatory vaccination rate on improving influenza vaccination among healthcare workers in 2021 – 2022 influenza season.   Methods  We conducted a non-randomized community intervention trial on influenza vaccination among healthcare workers in 7 hospitals in Nanshan district of Shenzhen city during an influenza season from October 2021 to April 2022. Free on-site influenza vaccination and prompt publicity for the vaccination were carried out among all the participants; compared to the 2 139 control participants in 3 hospitals, an additional dissemination about the expected non-mandatory vaccination rate of 80% and 60% for the staff working in departments assessed as at high- and low-risk of influenza infection was implemented among 4 599 participants in 4 hospitals of the intervention group. Pearson′s chi-squared test for adjusted ratio estimators was used to test the baseline and post-intervention vaccination rates for the intervention and control group.   Results  Over the influenza season for the participants working in high-risk departments, the influenza vaccination rate was 62.67% and 23.71% in the intervention and the control group, with a significant absolute rate difference (ARD) of 38.96% (95% confidence interval: 14.17% – 63.75%) between the two groups (P < 0.05); for the participants of low-risk departments, the influenza vaccination rate was 34.57% and 22.96% in the intervention and the control group(P > 0.05); for all the participants, the influenza vaccination rate was 43.90% and 23.19% in the intervention and in the control group (P > 0.05). The intervention of dissemination about the expected vaccination rate showed a significant impact upon the influenza vaccination rate for the participants working in high-risk departments but not for those in low-risk departments.   Conclusion  Under the premise of without both reward and punishment for having influenza vaccination, the dissemination of a high expected non-mandatory vaccination rate may increase the influenza vaccination rate among healthcare workers intervened.
Influenza vaccine effectiveness in primary and secondary school students: an ILI surveillance-based test-negative design case-control study in a district of Shenzhen city during 2021 – 2022 influenza season
JIANG Shiqiang, PENG Mingji, CAooI Yuwei,
, Available online  , doi: 10.11847/zgggws1140344
Abstract(133) HTML (23) PDF 473KB(42)
  Objective  To evaluate the vaccine effectiveness (VE) of inactivated trivalent influenza vaccine in primary and secondary school students.   Methods  Respiratory specimens were detected with PCR for influenza virus nucleic acid among 286 primary and secondary school students (6 – 15 years old) diagnosed as influenza-like illness (ILI) cases at all fever clinics in Nanshan district of Shenzhen city during an influenza season (from November 2021 to May 2022) and the ILI cases’ information on demography and influenza vaccination were collected simultaneously. The ILI cases positive for viral nucleic acid were assigned into a case group and those negative into a control group. Influenza vaccination ratio and odds ratio [OR] of viral nucleic acid positive the two groups were analyzed and compared to estimate the VE of influenza vaccination.   Results  Of the 286 ILI cases, 68 (23.78%) were positive for influenza nucleic acid (all belonging to B strain) and 218 (76.22%) were negative. The ratio of seasonal influenza vaccination was 5.88% (4/64) for the cases and 15.14% (33/216) for the controls, and the OR of being virus nucleic acid positive was 0.3886 (95% confidence interval [CI]: 0.1528 – 0.9880) for the vaccinated ILI cases. The estimated VE was 61.14% (95%CI: 1.20% – 84.72%) for seasonal influenza vaccination.   Conclusion  Seasonal influenza vaccination can protect primary and secondary school students from influenza virus infection. The result suggests that seasonal influenza vaccination needs to be promoted among the school age children.
Epidemiological characteristics of influenza-like illness during 2021 – 2022 in Xiamen city: a hospital-based sentinel surveillance data analysis
REN Min, REN Beile, ZHANG Junneng
, Available online  , doi: 10.11847/zgggws1140813
Abstract(200) HTML (78) PDF 479KB(36)
  Objective  To 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.   Results  Of 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% (n = 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.   Conclusion  According 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.
Epidemiological characteristics and outbreak management of influenza in Yunnan province, 2010 – 2021
SHEN Xiulian, ZHENG Erda, HUANG Tian,
, Available online  , doi: 10.11847/zgggws1140233
Abstract(115) HTML (34) PDF 625KB(38)
  Objective  To analyze epidemiological characteristics and outbreak management of influenza in Yunnan province and to provide evidence for developing effective prevention and control strategies.   Methods  The data on reported influenza cases and outbreaks in Yunnan province during 2010 – 2021 were collected from China Information System for Disease Control and Prevention and analyzed using descriptive statistics.   Results  Totally 85 018 influenza cases and 13 deaths were reported in the province during the 12-year period, with the average annual incidence of 14.9895/100 000. Although the cases were reported in populations of various ages, the majority (52.64%) of the cases were at ages of 0 – 9 years and only 7.18% of the cases were elderly people aged ≥ 60 years. The top three average annual influenza incidence (82.7681, 37.9560, and 34.1800 per 100 100 population) were observed in three prefectures, namely Dehong, Honghe and Diqing). There were altogether 16 000 reported cases with laboratory confirmation, of them, 50.99% and 48.14% had influenza A and B virus infection, and 0.87% had combined infection of influenza A and B. Among 127 influenza outbreaks identified during the period in the province, 120 occurred in schools; 64 and 54 caused by influenza B and A virus infection, and 9 were induced by combined infection of influenza A and B virus. For the outbreaks, the average total number of reported cases in one outbreak was 69.6; the interval between the report of first case and the identification of the outbreak ranged 4.5 – 10 days; and the median duration of the outbreaks was 12 days (25th, 75 th percentile: 8, 19). The interval between the report of first case and the identification of an outbreak was positively correlated with the duration of the outbreak (rS = 0.518, P < 0.05).   Conclusion  During 2010 – 2021 in Yunnan province, influenza was prevalent from November of a year to January of the next year, especially among children aged 0 – 9 years and the most of the influenza outbreaks occurred in schools, suggesting that influenza vaccination should be promoted among high-risk populations to control the epidemic in the province.