Positive Rate Of Influenza Virus Research Articles

Analysis of the epidemiological characteristics and genetic characteristics of influenza in the surveillance-year of 2021 to 2022 in Shandong Province, China

Objective: To analyze the epidemiological characteristics, etiology and hemagglutinin (HA) gene characteristics of prevalent strains in Shandong Province from 2021 to 2022. Methods: The sentinel surveillance data of influenza-like illness (ILI) were collected in Shandong Province from 2021 to 2022. ILI specimens were detected with Real-Time PCR and virus isolation to explore the distribution of influenza viruses in different months. Three virus strains of each city were selected for gene sequencing, and the HA phylogenetic analysis was carried out. Results: In the surveillance-year from 2021 to 2022, 528 263 ILI cases were totally reported in 54 sentinel hospitals for influenza surveillance in Shandong Province. ILI visiting ratio (ILI%) was 4.07%, with the largest number in 0-4 age group (45.86%). The highly frequent season for ILI was in winter and spring, with a peak in the 52nd week, 2021 (6.62%). Totally, nucleic acid was detected in 26 754 specimens, with a positive rate of 27.10%, all of which were type B Victoria influenza. The positive rate reached a peak in the 49th week, 2021 (63.78%). A total of 295 outbreaks of ILI had been reported, in which 269 were positive for influenza virus. Most of outbreaks occurred in the primary school, with a peak in December. Gene evolution analysis showed that the HA gene in Shandong possessed high homology, 98.6% to 99.5%, with the recommended vaccine strains in 2020-2023, which was divided into two branches, V1A.3a.1 and V1A.3a.2. Conclusion: In the surveillance-year of 2021-2022, influenza is prevalent in December in Shandong Province, with a single circulating strain type. The positive rate of influenza virus and outbreak are higher than those in the previous surveillance-year. The circulating strain possesses high HA gene homology with those of the WHO vaccine recommended strains. However, the overall immune barrier of influenza virus is weak.

Pilot Influenza Syndromic Surveillance System Based on Absenteeism and Temperature in China: Development and Usability Study.

BackgroundShortcomings of the current school-based infectious disease syndromic surveillance system (SSS) in China include relying on school physicians to collect data manually and ignoring the health information of students in attendance.ObjectiveThis study aimed to design and implement an influenza SSS based on the absenteeism (collected by face recognition) and temperature of attending students (measured by thermal imaging).MethodsAn SSS was implemented by extending the functionality of an existing application. The system was implemented in 2 primary schools and 1 junior high school in the Yangtze River Delta, with a total of 3535 students. The examination period was from March 1, 2021, to January 14, 2022, with 174 effective days. The daily and weekly absenteeism and fever rates reported by the system (DAR1 and DFR; WAR1 and WFR) were calculated. The daily and weekly absenteeism rates reported by school physicians (DAR2 and WAR2) and the weekly positive rate of influenza virus (WPRIV, released by the Chinese National Influenza Center) were used as standards to evaluate the quality of the data reported by the system.ResultsAbsenteeism reported by school physicians (completeness 86.7%) was 36.5% of that reported by this system (completeness 100%), and a significant positive correlation between them was detected (r=0.372, P=.002). When the influenza activity level was moderate, DAR1s were significantly positively correlated among schools (rab=0.508, P=.004; rbc=0.427, P=.02; rac=0.447, P=.01). During the influenza breakout, the gap of DAR1s widened. WAR1 peaked 2 weeks earlier in schools A and B than in school C. Variables significantly positively correlated with the WPRIV were the WAR1 and WAR2 of school A, WAR1 of school C, and WFR of school B. The correlation between the WAR1 and WPRIV was greater than that between the WAR2 and WPRIV in school A. Addition of the WFR to the WAR1 of school B increased the correlation between the WAR1 and WPRIV.ConclusionsData demonstrated that absenteeism calculation based on face recognition was reliable, but the accuracy of the temperature recorded by the infrared thermometer should be enhanced. Compared with similar SSSs, this system has superior simplicity, cost-effectiveness, data quality, sensitivity, and timeliness.

Effects of Different Absenteeism Statistical Methods on Influenza Surveillance

<i>Background</i> The existing absenteeism surveillance systems in China rely heavily on school doctors to collect data manually, but the low prevalence rate of school doctors makes it difficult to popularize this mode. The method of absenteeism statistics requires new breakthroughs. <i>Objective</i> The purpose of this study was to evaluate the feasibility of an established absenteeism surveillance system based on face recognition, and to explore the appropriate surveillance index for this system. <i>Methods</i> A primary school of about 1900 students was selected. Absenteeisms reported by school doctors and this system from March 1, 2021 (week 9) to January 14, 2022 (week 2) were collected, as well as weekly positive rate of influenza virus (WPRIV) released by China National Influenza Center. Eight weekly absenteeism rate indicators were calculated: all-cause absenteeism rate reported by system (WAR1), all-cause absenteeism rate reported by school doctors (WAR2), sickness absenteeism rate reported by school doctors (WAR3), and the rate of students absent one time (WAR4), two times (WAR5), three to four times (WAR6), one to two times (WAR7) and two to four times (WAR8) a week reported by the system. Pearson correlation coefficients of eight indicators and WPRIV were analyzed, and the change trend of their time series diagram was investigated. <i>Results</i> During week 9-42, WAR1 (r=0.614, p=0.001), WAR4 (r=0.631, p<0.001), WAR5 (r=0.651, p<0.001), WAR6 (r=0.541, p<0.001), WAR7 (r=0.654, p<0.001) and WAR8 (r=0.644, p<0.001) were significantly correlated with WPRIV, while WAR2 (r=0.262, p>0.05) and WAR3 (r=0.239, p>0.05) were not. Throughout the surveillance period, WAR1 (r=0.671, p<0.001), WAR2 (r=0.638, p<0.001), WAR3 (r=0.752, p<0.001), WAR5 (r=0.682, p<0.001), WAR6 (r=0.535, p<0.001) and WAR8 (r=0.683, p<0.001) were significantly correlated with WPRIV, while WAR4 (r=0.086, p>0.05) and WAR7 (r=0.242, p>0.05) were not. <i>Conclusions</i> Absenteeism reported by the system was more effective for influenza surveillance than absenteeism reported by school doctors, especially when the influenza activity level was low. When WAR1, WAR5 and WAR8 were combined together, the epidemic situation of influenza could be more comprehensively aware.

Impact of non-pharmaceutical interventions during the COVID-19 pandemic on common childhood respiratory viruses – An epidemiological study based on hospital data

Considering common childhood respiratory viruses and SARS-CoV-2 share similar transmission routes, non-pharmaceutical interventions (NPIs) to prevent SARS-CoV-2 may affect the epidemiology of respiratory viruses. Therefore, our study aimed to observe the epidemiologic characteristics of common childhood respiratory viruses in 2020 (after the pandemic) compared with 2019 (before the pandemic) in Hangzhou, China. The data were compared between 2019 and 2020 based on age and month, respectively. One or more viruses were detected in 3135/21452 (14.61%) specimens in 2019, which was significantly lower in 1110/8202 (13.53%) specimens in 2020. Respiratory syncytial virus (RSV) was the most commonly detected virus in 2019 and 2020. The positive rate of adenovirus (ADV), parainfluenza virus (PIV)1, PIV2, and PIV3 in 2020 was significantly decreased in 2019. In 2020, RSV replaced ADV as the most predominant virus in children aged 1–6 years, and the positive rate of influenza virus A (FluA), influenza virus B (FluB), PIV1, and PIV2 was not correlated to age. FluA, FluB, and PIV2 were not almost detected from February 2020. The positive rates of ADV and PIV1 were uncorrelated to the month in 2020. By strict NPIs, besides controlling the COVID-19 pandemic, incredible progress has been made to reduce the prevalence of common childhood respiratory viruses.

Viral pathogenic spectrum analysis of severe acute respiratory infection cases in Luohe City, Henan province from 2017 to 2019

Objective: The purpose of this study was to investigate the characteristics of viral pathogen spectrum and the epidemiological characteristics of each viral pathogen in hospitalized cases associated with severe acute respiratory infection (SARI) in Luohe City, Henan Province from 2017 to 2019. Methods: Based the SARI Case Surveillance Platform, SARI cases were collected in Central Hospital of Luohe City, Henan Province from November 2017 to February 2019. In the end, 783 SARI cases were included, whose throat swabs were taken within 24 h of admission, as well as their demographic characteristics, onset time, clinical characteristics and other information recorded. At the same time, viral identification was performed, and the age and time distribution of each virus were analyzed. Results: The age of 783 SARI cases shown as M (P25, P75) was 3 (1, 5) years old, ranging from 1 month to 95 years old. Children under 5 years old were the majority (71.01%). The males (61.81%) were more than females (38.18%). Among the 783 SARI cases, a total of 9 kind of viruses were identified with 64.88% (508/783) of the throat swabs tested positive for at least one virus. The positive rate of influenza virus and human respiratory syncytial virus were both 20.18% (158 cases), which was the highest among all the detected respiratory virus. The co-infection rate was 15.84% (124/783), among which double infection was the most common, accounting for 85.48% (106/124) of the co-infected cases. And human respiratory syncytial virus, human rhinovirus and influenza virus were the most common pathogen in co-infection cases. Moreover, the viral positive rate was 68.71% in children aged 5 years and 63.27% in people aged 60-95 years. Influenza and human respiratory syncytial virus dominated in winter and spring, while human parainfluenza virus was the main infection in summer. Conclusion: Influenza virus and human respiratory syncytial virus were the main viruses in throat swabs of SARI cases from 2017 to 2019 in Luohe City, Henan Province. There were differences in the age and seasonal epidemiological characteristics of each virus.

Evaluation of the application of moving epidemic method on making influenza epidemic thresholds in the 7 climate zones in China

Objective: We planned to evaluate the effectiveness of moving epidemic method (MEM) in calculating influenza epidemic threshold of 7 climatic zones in China mainland. Methods: The positive rate of influenza virus was obtained from the National Influenza Surveillance Network System from 2010/2011 to 2017/2018. We divided the 31 provinces into 7 climatic zones according to previous literatures and applied MEM to calculate the influenza epidemic threshold of 2018/2019 influenza season for these climatic zones. Sensitivity, specificity, positive predictive value and negative predictive value were calculated to evaluate the effectiveness of MEM. Results: Pre-epidemic threshold (the positive rate of influenza virus) varied from 9.66% (temperate zone) to 16.36% (subtropical zone) for 2018/2019 influenza season. The gap between pre-epidemic and post-epidemic thresholds was less than 5% except for plateau zone. The sensitivity was 86.16% (95CI:66.81%-98.23%), the specificity was 94.92% (95CI: 91.13%-98.41%), the positive predictive value was 89.87% (95%CI: 84.39%-94.38%), the negative predictive value was 92.96% (95%CI: 84.46%-99.17%). Conclusion: Overall, moving epidemic Method performs well in calculating influenza epidemic threshold in China, much better than the previous study.

Epidemiology and ARIMA model of positive-rate of influenza viruses among children in Wuhan, China: A nine-year retrospective study

ObjectiveInfluenza is a common childhood disease and protecting children by predicting the positive rate of influenza virus is important as vaccines are not routinely administered in China. Our study aims to describe the epidemiology of influenza viruses among children in Wuhan, China during the past nine influenza seasons (2007–2015) and to predict the positive rate of different types of influenza virus in the future. MethodsDuring the last nine influenza seasons (2007–2015), a total of 10,232 nasopharyngeal swabs collected from pediatric outpatients (age <15years) with influenza-like illness (ILI) infections in two sentinel children’s hospitals were examined for influenza A and B by real-time one step RT-PCR. An autoregressive integrated moving average (ARIMA) model was used to fit the time series and to predict the future (first half of 2016) positive rates of different types of influenza virus. ResultsA total of 1,341 specimens were positive for influenza A and 490 for influenza B. The majority of infected patients were 1–11 years old (87.7%). The ARIMA model could effectively predict the positive rate of influenza virus in a short time. ARIMA(0,0,11), SARIMA(1,0,0)(0,1,1)12, ARIMA(0,0,1) and SARIMA(0,0,1)(1,0,1)12 were suitable for B(Victoria), B(Yamagata), A(H1N1)pdm09, and A(H3N2), respectively. ConclusionAdditional policies must be formulated to prevent and control influenza. The wide use of influenza vaccines, especially for influenza B, especially for influenza B(Yamagata) and B(Victoria), can potentially reduce the effects of influenza on children of China.

Study on seasonal characteristics and pathogenic distribution of influenza in Gansu province of China

Objective: To study the epidemiologic characteristics of influenza in Gansu province of China and to optimize the related vaccination program. Methods: Weekly influenza surveillance data from the first week of 2010 to the fortieth week of 2016 were collected, in Gansu province. χ(2) test was used to compare the differences of nucleic acid positive rate and the virus types in the four seasons. Time series seasonal decomposition (TSSD) was used to explore seasonal patterns and characteristics of influenza epidemics in Gansu. Results: 59 791 specimens were tested, with 8 501 positive for influenza virus and positive rates as 14.22%. Types A(H1N1)pdm09, A(H3N2) and type B were accounted for 98.76% of all the positive specimens. Proportions of the positive rate of influenza virus appeared in spring, summer, autumn and winter were 15.12%, 0.98%, 4.02% and 24.26% respectively. The predominant type of virus in autumn and winter was A(H3N2), with B mainly in spring. Influenza in Gansu province showed typical single-peak type distribution, with epidemic peak appeared from December to next January. The type A(H3N2) related peak appeared the earliest, followed by A(H1N1) pdm09, with type B the latest. Conclusions: Peaks and the duration of influenza seasonal epidemics were related to the types of dominant strains. Annual influenza vaccination campaigns should start in October, to provide effective protection during the epidemic period.

Clinical characteristics of hospitalized severe acute respiratory illnesses (SARI) in children and risk factors analysis of severe illness: results from SARI patients under 15-year-old of sentinel surveillance in 10 cities, China

To investigate clinical and epidemiological characteristics of hospitalized severe acute respiratory illnesses (SARI) patients under 15 years old registered by sentinel hospitals at 10 cities and risk factors analysis of severe illness. The objects of this study were 2 937 SARI patients under 15 years old registered by sentinel surveillance in internal wards, pediatrics wards and intensive care units (ICU) of 10 sentinel hospitals in 10 cities during the period from December 2009 to June 2014. We also collected case report form (CRF) of them and their throat swabs for influenza testing. The inclusion criteria was hospitalized patients who were admitted by surveillance departments, registered by SARI surveillance system, under 15 years old, meeting SARI case definition and with complete CRF. Rank-sum test was used to compare the difference of age, the duration including from onset to admission, hospital stay and from onset to discharging/death between mild illness and severe illness. Chi-square test was used to compare the difference of demographic characteristics, influenza psoitive rate, vaccination rate of influenza, chronic medical conditions and clinical characteristics between mild illness and severe illness. Logistic regression was used to analysis risk factors associated with severe illness by two stratifications from SARI surveillance protocol (< 2 years old and ≥ 2 years old). Among 2 937 SARI patients under 15 years old, 97.7% (2 872/2 937) was mild illnesses, and 2.3% (65/2 937) was severe illnesses. 78.8% (2 315/2 937) was under 5 years old. The median ages of severe illness and mild illness were 0.4 and 2.0 years old (U = -6.23, P < 0.001). The proportions of severe illness and mild illness with at least one chronic medical condition were 32.3% (21/65) and 8.4% (240/2 872) (χ² = 45.03, P < 0.001). The positive rate of influenza virus was 6.5% (190/2 937), which was 6.5% (186/2 858) for mild illness and 6.2% (4/65) for severe illness (χ² = 0.08, P = 0.961). The proportion of seasonal influenza vaccination was 1.5% (42/2 853), which was 1.5% (42/2 788) for mild illness and higher than that for severe illness (0) (χ² = 6.09, P = 0.048). For under 2 years old patients, age < 11 months and with at least one chronic medical condition were risk factors for severe SARI illness, and the risk for SARI patients who was 12-23 months and without medical condition was 14.71 (5.35-40.44) and 5.61 (2.96-10.63). For ≥ 2 years old patients, age, with at least one chronic medical condition and seasonal influenza vaccination history have no association with severe illness, OR (95% CI) was 0.92 (0.80-1.05), 0.67 (0.09-5.05) and 0.85 (0.31-2.35), respectively. Most of SARI patients registered by 10 urban sentinel hospitals were patients under 5 years old. Age < 11 months and with at least chronic medical conditions were possible risk factors of severe illness of SARI patients.

Viral aetiology of acute lower respiratory tract illness in hospitalised paediatric patients of a tertiary hospital: One year prospective study

Context: Acute lower respiratory tract infections (ALRI), ranked as the second leading cause of death are the primary cause of hospitalisation in children. Viruses are the most important causative agents of ALRI. Aim: To study the viral aetiology of ALRI in children at a tertiary care hospital. Setting and Design: One year prospective observational study in a tertiary care hospital of King George’s Medical University, Lucknow. Material and Methods: Nasopharyngeal aspirate (NPA) was collected from children admitted with signs and symptoms of ALRI who were aged 0-14 years. Samples were transported to the laboratory at 4°C in viral transport media and processed for detection of respiratory syncytial virus (RSV) A and B, influenza virus A and B, adenovirus (ADV), human Boca virus (HBoV), human metapneumo virus (hMPV) and parainfluenzavirus 1, 2, 3 and 4 using mono/multiplex real-time polymerase chain reaction (RT-PCR). STATA was used for statistical analysis. Results: In one year, 188 NPAs were screened for respiratory viruses, of which 45.7% tested positive. RSV was most commonly detected with 21.3% positivity followed by measles virus (8.5%), influenza A virus (7.4%), ADV (5.3%), influenza B virus (1.6%), hMPV (1.1%) and HBoV (0.5%). Month wise maximum positivity was seen in December and January. Positivity rate of RSV was highest in children aged < 1 year, which decreased with increase in age, while positive rate of influenza virus increased with increasing age. Conclusion: The occurrence of viral predominance in ALRI is highlighted.

Epidemiological characteristics of influenza virus and respiratory syncytial virus among children in Wuhan area from 2008 to 2012

To investigate the infection status and epidemiological characteristics of influenza virus and respiratory syncytial virus (RSV) in influenza-like illness (ILI) of children ( ≤ 14 years) in Wuhan area from 2008 to 2012. A total of 2854 cases of ILI patients ( ≤ 14 years) in a hospital of Wuhan were recruited in the study from July 2008 to June 2012. The sample of pharyngeal swab was collected from each patient, to extract the virus nucleic acids. Real-time fluorescent quantitation reverse transcription PCR (RT-PCR) method was applied to detect the subtypes of influenza virus and RSV, and then analyzed the time and age characteristics. Out of the 2854 cases, 758 (26.6%) were positive for influenza virus,including 547 (19.2%) influenza A virus positive samples and 211 (7.4%) influenza B virus positive samples. Usually, there were two peaks present in the annual curve of influenza virus, namely summer peak and winter/spring peak. The positive rate of influenza virus in 6-14 years old children (48.0%, 275/573) was significantly higher than that in 3-5 years old children (26.6%, 213/801) and that under 3 years old children (18.3%, 270/1480). The difference showed statistical significance (χ(2) = 187.432, P < 0.01). A total of 219 (7.7%) cases were positive for RSV,including 108 RSV-A positive samples and 112 RSV-B positive samples (1 co-infection). The epidemic of RSV showed an obvious seasonal pattern with peaks in autumn,winter and spring,which accounted for 96.8% (212/219) of all the cases; however, the annual incidence of RSV fluctuated greatly. The predominant subtype shifted every 2 years. RSV-B predominated during September 2008 and May 2009, December 2009 and March 2010, accounting for 76.6% (36/47) and 96.9% (62/64) respectively. RSV-A predominated during November 2010 and March 2011, September 2011 and April 2012, accounting for 92.5% (37/40) and 100.0% (48/48) respectively. With the increase of the age, the positive rate of RSV-A and RSV-B decreased gradually (RSV-A: χ(2) = 36.223, P < 0.01; RSV-B: χ(2) = 36.281, P < 0.01). The positive rates of RSV-A in children < 1,1,2,3,4,5-9 and 10-14 years old were 7.0% (26/373), 5.9% (39/662), 4.0% (18/445), 3.2% (13/406), 1.3% (3/236), 1.4% (7/517) and 0.9% (2/215) respectively; while, the positive rates of RSV-B in each age group were 6.4% (24/373), 6.0% (40/662), 4.5% (20/445), 4.4% (18/406), 1.3% (3/236), 1.0% (5/517) and 0.9% (2/215) respectively. The children aged 0-3 years old were more susceptible for RSV infection,accounting for 90.0% (197/219) of the total positive samples. During the outbreak of influenza A H1N1 in November 2009, the positive rate of RSW was 3.0% (3/100), lower than that in the same month of 2008, 2010 and 2011,which were separately 18.2% (6/33), 10.8% (10/93) and 10.0% (4/40). The difference showed statistical significance (χ(2) = 8.450, P < 0.05). During the outbreak of influenza A (H1N1) in January 2011,the positive rate of RSV was 5.7% (3/53), lower than those in the same month of 2009, 2010 and 2012, which was separately 21.7% (5/23), 28.6% (22/77) and 16.0% (8/50). The difference showed statistical significance (χ(2) = 11.233,P < 0.05). During the period of less influenza happened in September 2011, the RSV positive rate was 25.0% (10/40), higher than those in the same month of 2008, 2009 and 2010, which was separately 11.4% (4/35), 1.7% (2/118) and 0.0% (0/109). The difference showed statistical significance (χ(2) = 32.521, P < 0.01). Both influenza virus and RSV were important etiological agents of ILI of children in Wuhan. The characteristics of seasonal and age distributions of the two viruses were notably different; meanwhile, a certain inhibitional effect of influenza virus on RSV could be observed.

Etiology and Clinical Characteristics of Influenza-Like Illness (ILI) in Outpatients in Beijing, June 2010 to May 2011

BackgroundSince May 2009, exposure of the population of Beijing, China to pH1N1 has resulted in an increase in respiratory illnesses. Limited information is available on the etiology and clinical characteristics of the influenza-like illness (ILI) that ensued in adults following the pH1N1 pandemic.MethodsClinical and epidemiological data of ILI in adults was collected. A total of 279 throat swabs were tested for twelve respiratory viruses using multiplex RT-PCR. Clinical characteristics of influenza A in outpatients versus test-negative patients were compared using Pearson's χ2 and the Mann-Whitney U test. 190 swabs were tested for pH1N1 by virus isolation. Consultation rates for ILI were compared between 2009 and 2010.ResultsOne or two virus were detected in 29% of the samples. Influenza A virus (FLU-A) accounted for 22.9% (64/279). Other viruses were present at a frequency less than 3.0%. Cough was significantly associated with Influenza A virus infection (χ2, p<0.001). The positive rate of FLU-A was consistent with changes in the ILI rate during the same period and there was a significant reduction in the incidence of ILI in 2010 when compared to 2009. During the 2010–2011 influenza season, the incidence peaked in January 2011 in Beijing and north China.ConclusionsExposure to pH1N1 had no impact on typical influenza seasonal peaks, although FLU-A remained the predominant virus for 2010 in Beijing. Symptomatically, cough was associated with FLU-A infection. The positive rate of influenza virus was consistent with changes in the ILI rate during the same period and there was a significant reduction in the incidence of ILI in 2010 when compared to that of 2009.