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Objective The aim is to analyze the spatial epidemiological characteristics for human infection with avian influenza H7N9 in Fujian Province, so as to provide scientific evidence for developing and adjusting related control strategies. Methods The epidemiological data of human infection with H7N9 avian influenza in Fujian Province, from 2013 to 2017 was analyzed by SAS 9.2, ArcGIS 10.3 and SaTScan 9.4 software.Results There were a total of 108 cases and 28 deaths reported in Fujian Province, up to December 31, 2017. The case fatality rate was 25.93%.96.30% of cases were sporadic. There were more incidences in winters and springs, more incidences in rural areas. The global spatial autocorrelation and high/low clustering analysis indicated that clusters at the county level were in the shore areas (Z=3.74, P<0.001; Z=5.26, P<0.001). The cities of Changle, Fuqing, Jinjiang and Siming were the high-high clustered areas and local hot-points. There were two clusters, from December 2014 to March 2015, the most likely cluster regions was centered around Zhangpu County with a radius of 63.04 km (RR=4.72, LLR=11.41, P<0.001). The secondary cluster regions was centered around Fuqing City with a radius of 81.98 km (RR=4.07, LLR=7.96, P=0.037). Conclusions Human infection with avian influenza H7N9 in Fujian Province is spatially and temporally clustered. The measures of prevention and control should be focused on high incidence seasons and key regions, and the surveillance of etiology should be strengthened.
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The number of H7N9 bird flu cases was high and the situation was grim in guizhou province in 2017. To understand the molecular characteristics of the hemagglutinin gene (HA) and the risk of human infection with avian influenza virus A(H7N9) in Guizhou Province, 2017. Homology, genetic evolution and pivotal sites related to receptor binding regions, pathogenicity and potential glycosylation of 14 avian influenza viruses A(H7N9) were analyzed by a series of bioinformation softwares. It was cleared that there was 95.9%-100% similarity among 14 strains in nucleotide of the HA gene, and there were 96.8%-97.8% and 96.8%-97.9% similarities with vaccine strains A/Shanghai/2/2013 and A/Anhui/1/2013 recommended by WHO, respectively. Phylogenetic analysis showed that 14 HA genes were directly evolved in the Yangtze River Delta evolution branch, but they could be derived from five diffenrent strains. Then 13 of 14 strains cleavage site sequences of HA protein revealed they were low pathogenic avian influenza viruses, while A/Guizhou-Weining/CSY01/2017 was high pathogenic avian influenza virus. Mutation G186V at the receptor binding sites in the HA was found in all 14 strains, and mutation Q226L in 13 strains besides A/Guizhou-Weining/CSY01/2017. All five potential glycosylation motifs in the HA were conservative.
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Objective To understand the molecular characteristics of hemagglutinin (HA) and neuraminidase (NA) as well as the disease risk of influenza virus A H7N9 in Guizhou province.Methods RNAs were extracted and sequenced from HA and NA genes of H7N9 virus strains obtained from 18 cases of human infection with H7N9 virus and 6 environmental swabs in Guizhou province during 2014-2017.Then the variation and the genetic evolution of the virus were analyzed by using a series of bioinformatics software package.Results Homology analysis of HA and NA genes revealed that 2 strains detected during 2014-2015 shared 98.8％-99.2％ and 99.2％ similarities with vaccine strains A/Shanghai/2/2013 and A/Anhui/1/2013 recommended by WHO,respectively.Two strains detected in 2016 and 14 strains detected in 2017 shared 98.2％-99.3％ and 97.6％-98.8％ similarities with vaccine strain A/Hunan/02650/2016,respectively.Other 6 stains detected in 2017 shared 99.1％-99.4％ and 98.9％-99.3％ similarities with strain A/Guangdong/17SF003/2016,respectively.Phylogenetic analysis showed that all the strains were directly evolved in the Yangtze River Delta evolution branch,but they were derived from different small branch.PEVPKRKRTAR ↓ GLF was found in 6 of 24 strains cleavage site sequences of HA protein,indicating the characteristic of highly pathogenic avian influenza virus.Mutations A134V,G186V and Q226L at the receptor binding sites were found in the HA.All the strains had a stalk deletion of 5 amino acid residue "QISNT" in NA protein,and drug resistance mutation R294K occurred in strain A/Guizhou-Danzhai/ 18980/2017.In addition,potential glycosylation motifs mutations NCS42NCT were found in the NA of 9 of 24 strains.Condusions HA and NA genes of avian influenza A (H7N9) virus showed genetic divergence in Guizhou province during 2014-2017.The mutations of key sites might enhance the virulence of the virus,human beings are more susceptible to it.Hence,the risk of infection is increasing.
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Objective To investigate the infection pattern and etiological characteristics of a case of human infection with highly pathogenic avian influenza A (H7N9) virus and provide evidence for the prevention and control of human infection with highly pathogenic avian influenza virus.Methods Epidemiological investigation was conducted to explore the case's exposure history,infection route and disease progression.Samples collected from the patient,environments and poultry were tested by using real time reverse transcriptase-polymerase chain reaction (RT-PCR).Virus isolation,genome sequencing and phylogenetic analysis were conducted for positive samples.Results The case had no live poultry contact history,but had a history of pulled chicken processing without taking protection measure in an unventilated kitchen before the onset.Samples collected from the patient's lower respiratory tract,the remaining frozen chicken meat and the live poultry market were all influenza A (H7N9) virus positive.The isolated viruses from these positive samples were highly homogenous.An insertion which lead to the addition of multiple basic amino acid residues (PEVPKRKRTAR/GL) was found at the HA cleavage site,suggesting that this virus might be highly pathogenic.Conclusions Live poultry processing without protection measure is an important infection mode of "poultry to human" transmission of avian influenza viruses.Due to the limitation of protection measures in live poultry markets in Guangzhou,it is necessary to promote the standardized large scale poultry farming,the complete restriction of live poultry sales and centralized poultry slaughtering as well as ice fresh sale.
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Objective To understand the epidemiological characteristics of human infection with avian influenza A (H7N9) virus in China,and provide evidence for the prevention and control of human infection with H7N9 virus.Methods The published incidence data of human infection with H7N9 virus in China from March 2013 to April 2017 were collected.Excel 2007 software was used to perform the analysis.The characteristics of distribution of the disease,exposure history,cluster of the disease were described.Results By the end of April 2017,a total of 1 416 cases of human infection with H7N9 virus were confirmed in China,including 559 deaths,the case fatality rate was 39.5％.In 2016,the case number was lowest (127 cases),with the highest fatality rate (57.5％).The first three provinces with high case numbers were Zhejiang,Guangdong and Jiangsu.The median age of the cases was 55 years and the male to female ratio was 2.3 ∶ 1.Up to 66％ of cases had clear live poultry exposure history before illness onset,31％ of cases had unknown exposure history and only 3％ of the cases had no live poultry exposure history.There were 35 household clusters (5 in 2013,9 in 2014,6 in 2015,5 in 2016,10 in 2017),which involved 72 cases,accounting for 5％ of the total cases.Conclusions The epidemic of human infection with H7N9 virus in China during 2013-2017 had obvious seasonality and spatial distribution.There was limited family clustering.Infection cases were mostly related to poultry contact.
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Objective@#To analyze epidemiological and genetic characteristics of the fifth avian influenza A (H7N9) wave in Suzhou, and to provide scientific basis for prevention and control of H7N9 virus infection.@*Methods@#Respectively, influenza A/B, H1N1 (pdm09), H3, H5N1, and H7N9 real-time PCR kits were used to detected pharyngeal swab samples which were collected from severe acute respiratory syndrome infection (SARI) cases in Suzhou. The H7N9-positive samples were further examined for virus isolation and gene sequencing.@*Results@#The H7N9 virus was mainly prevalent in winter in Suzhou City. In the fifth H7N9 virus epidemic, the overall fatality rate of human infection with H7N9 virus in Suzhou city was 40% (22/55). Additionally, most were older people (median age was 58 years) and more than 80% of H7N9 patients had live poultry exposure history. The nucleic acid homology of HA gene was 98.7-100%. There were no mutations in the key sites of the HA gene sequence.@*Conclusions@#The H7N9 virus can not be effectively spread in the crowd currently, with no significant changes in receptor binding sites (RBS). In addition, exposure to live poultry or contaminated environment is still the main source of human infection with H7N9. At present, the viruses circulating in Suzhou city are low pathogenic to poultry.
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Objective@#To investigate the molecular characteristics and tracing of the hemagglutinin (HA) gene, and to analyze the risk of human infection with influenza virus A (H7N9) in Guizhou Province, so that to provide evidence for the prevention and control of highly pathogenic avian influenza A (H7N9).@*Methods@#Nucleic acids of 5 strains of H7N9 including 1 sample of the patient′s nasopharyngeal swab and 4 samples of the live poultry market (LPM) environment were extracted and HA genes were amplified and sequenced. Then the homology, genetic evolution and the pivotal sites related to receptor binding regions, pathogenicity and potential glycosylation of the avian influenza A (H7N9) viruses were analyzed by a series of bioinformatics softwares.@*Results@#Homology analysis revealed that the homologies of nucleotide and amino-acid of the HA gene of H7N9 strains from the patient and LPM in Weining County, Guizhou Province were 99.8% and 99.6%, respectively, while those of 4 strains from LPM were both 100%. The homologies of nucleotide and amino-acid of the HA gene of H7N9 strains were the highest with the strain of A/Guangxi/5/2017 isolated from a Guangxi infected patient (99.7%-99.9% and 99.4%-99.8%, respectively), while those with the strain isolated from LPMs environment at the end of 2016 (A/Environment/Guangdong/C16283222/2016) were 99.0%-99.2% and 98.9%-99.2%, respectively. However, the homologies of nucleotide and amino-acid of the HA gene of H7N9 strains with A/Shanghai/2/2013 recommended by world health organization and the candidate vaccine strain A/Anhui/1/2013 were 96.8%-97.0% and 95.8%-96.2%, respectively. Phylogenetic analysis showed that the 5 strains had the nearest genetic distance to the strain A/Guangxi/5/2017. All the 5 strains cleavage site sequences of HA protein showed mutation of PEVPKRKRTAR↓GLF, and they were highly pathogenic avian influenza viruses mutant strains, which all had mutation of G186V at the receptor binding sites of HA gene, while no Q226L mutation was found. All 5 strains had new mutation of A363S, and new mutations of R56K and I297V were only found in the strain isolated from the patient. Among the five potential glycosylation motifs in the HA, only 421NWT and 493NNT had variation of the position post shift.@*Conclusions@#All the 5 H7N9 strains isolated in Weining County, Guizhou Province are highly pathogenic avian influenza mutative viruses. The current candidate vaccine may not provide a very good protection. The mutations of cleavage site of HA protein, G186V as well as other new mutation sites of HA may enhance the susceptibility and pathogenicity to human beings.
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Human infection with avian influenza A (H7N9) is an acute contagious respiratory disease. Acute respiratory distress syndrome (ARDS) is a common complication in patients with severe avian influenza A (H7N9), for whom mechanical ventilation (MV) is an important supportive method. A patient, suffered from severe avian influenza A (H7N9) and complicated with ARDS, was admitted to the Second Affiliated Hospital of Guizhou Medical University in January 2017. With very intensive care for oxygenation, respiration and consciousness, and monitoring, she was successfully cured by comprehensive managements, among which noninvasive mechanical ventilation (NIV) was the major respiratory support method. The result demonstrate that, in patients with conscious state, satisfied expectoration ability and relatively good cooperation, and with close observation of oxygenation and respiratory rate, NIV may be accepted as an effective method for patient with ARDS caused by severe avian influenza A (H7N9).
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Human infection with avian influenza A (H7N9) is easy to induce severe acute respiratory distress syndrome (ARDS), and traditional mechanical ventilation cannot correct hypoxemia, so patients may die from multiple organ failure (MOF) caused by persistent hypoxia. Extracorporeal membrane oxygenation (ECMO) can provide effective respiratory support and win time for the treatment of severe H7N9. The first case of severe H7N9 in Guangdong Province in 2018 was admitted to Zhongshan Hospital Affiliated to Sun Yat-sen University. The case was insult with severe ARDS caused by H7N9, the traditional mechanical ventilation could not correct hypoxemia, and the lung condition gradually improved with ECMO assistance. After 13 days of ECMO support, the patient was successfully weaned from ECMO and was transferred to a general ward after 55 days. After 102 days of rehabilitation, the patient was discharged from hospital and followed up for 2 months, who was in good health and had a good quality of life. This article states the diagnosis and treatment of severe H7N9 in details, providing experience for the treatment of severe H7N9 in the future.
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Objective To understand the molecular characteristics of hemagglutinin (HA) and neuraminidase (NA) as well as the disease risk of influenza virus A H7N9 in Guizhou province.Methods RNAs were extracted and sequenced from HA and NA genes of H7N9 virus strains obtained from 18 cases of human infection with H7N9 virus and 6 environmental swabs in Guizhou province during 2014-2017.Then the variation and the genetic evolution of the virus were analyzed by using a series of bioinformatics software package.Results Homology analysis of HA and NA genes revealed that 2 strains detected during 2014-2015 shared 98.8％-99.2％ and 99.2％ similarities with vaccine strains A/Shanghai/2/2013 and A/Anhui/1/2013 recommended by WHO,respectively.Two strains detected in 2016 and 14 strains detected in 2017 shared 98.2％-99.3％ and 97.6％-98.8％ similarities with vaccine strain A/Hunan/02650/2016,respectively.Other 6 stains detected in 2017 shared 99.1％-99.4％ and 98.9％-99.3％ similarities with strain A/Guangdong/17SF003/2016,respectively.Phylogenetic analysis showed that all the strains were directly evolved in the Yangtze River Delta evolution branch,but they were derived from different small branch.PEVPKRKRTAR ↓ GLF was found in 6 of 24 strains cleavage site sequences of HA protein,indicating the characteristic of highly pathogenic avian influenza virus.Mutations A134V,G186V and Q226L at the receptor binding sites were found in the HA.All the strains had a stalk deletion of 5 amino acid residue "QISNT" in NA protein,and drug resistance mutation R294K occurred in strain A/Guizhou-Danzhai/ 18980/2017.In addition,potential glycosylation motifs mutations NCS42NCT were found in the NA of 9 of 24 strains.Condusions HA and NA genes of avian influenza A (H7N9) virus showed genetic divergence in Guizhou province during 2014-2017.The mutations of key sites might enhance the virulence of the virus,human beings are more susceptible to it.Hence,the risk of infection is increasing.
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Objective To investigate the infection pattern and etiological characteristics of a case of human infection with highly pathogenic avian influenza A (H7N9) virus and provide evidence for the prevention and control of human infection with highly pathogenic avian influenza virus.Methods Epidemiological investigation was conducted to explore the case's exposure history,infection route and disease progression.Samples collected from the patient,environments and poultry were tested by using real time reverse transcriptase-polymerase chain reaction (RT-PCR).Virus isolation,genome sequencing and phylogenetic analysis were conducted for positive samples.Results The case had no live poultry contact history,but had a history of pulled chicken processing without taking protection measure in an unventilated kitchen before the onset.Samples collected from the patient's lower respiratory tract,the remaining frozen chicken meat and the live poultry market were all influenza A (H7N9) virus positive.The isolated viruses from these positive samples were highly homogenous.An insertion which lead to the addition of multiple basic amino acid residues (PEVPKRKRTAR/GL) was found at the HA cleavage site,suggesting that this virus might be highly pathogenic.Conclusions Live poultry processing without protection measure is an important infection mode of "poultry to human" transmission of avian influenza viruses.Due to the limitation of protection measures in live poultry markets in Guangzhou,it is necessary to promote the standardized large scale poultry farming,the complete restriction of live poultry sales and centralized poultry slaughtering as well as ice fresh sale.
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Objective To understand the epidemiological characteristics of human infection with avian influenza A (H7N9) virus in China,and provide evidence for the prevention and control of human infection with H7N9 virus.Methods The published incidence data of human infection with H7N9 virus in China from March 2013 to April 2017 were collected.Excel 2007 software was used to perform the analysis.The characteristics of distribution of the disease,exposure history,cluster of the disease were described.Results By the end of April 2017,a total of 1 416 cases of human infection with H7N9 virus were confirmed in China,including 559 deaths,the case fatality rate was 39.5％.In 2016,the case number was lowest (127 cases),with the highest fatality rate (57.5％).The first three provinces with high case numbers were Zhejiang,Guangdong and Jiangsu.The median age of the cases was 55 years and the male to female ratio was 2.3 ∶ 1.Up to 66％ of cases had clear live poultry exposure history before illness onset,31％ of cases had unknown exposure history and only 3％ of the cases had no live poultry exposure history.There were 35 household clusters (5 in 2013,9 in 2014,6 in 2015,5 in 2016,10 in 2017),which involved 72 cases,accounting for 5％ of the total cases.Conclusions The epidemic of human infection with H7N9 virus in China during 2013-2017 had obvious seasonality and spatial distribution.There was limited family clustering.Infection cases were mostly related to poultry contact.
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Since March 2013,China had experienced five seasonal epidemics related to Avian influenza A (H7N9).An unprecedented outbreak of H7N9 epidemic started from September 2016,with 730 cases reported till June 30th 2017,in mainland China that caused profound influences on both social development and health of the people.As an emerging infectious disease,information on pathogenic characteristics,transmission patterns and other epidemiological features of H7N9 virus somehow remained unclear.Data from previous studies suggested that the live poultry market (LPM) seemed to have served as main places where H7N9 virus got originated,mutated,spread and thus infected the human beings.Hence,closure of LPMs was suggested a major measure to control and prevent H7N9 epidemics in China.However,the effectiveness of different ways of LPM closures on H7N9 epidemics had been controversial.This study systemically summarized the effects of different ways of LPM closures on H7N epidemics from previous studies,aiming to provide references for developing a better program on H7N9 control and prevention in the country.
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Objective To investigate human exposure to live poultry (poultry feeding and purchasing) in the residents in Beijing and related factors during the second wave of avian influenza A (H7N9) epidemic during 2013-2014, and provide scientific evidence for avian influenza prevention and control. Methods A total of 7366 adults aged ≥18 years were selected through multi-stage stratified sampling in Beijing for a questionnaire survey. Logistic regression model was used to analyze the influence factors of human exposure to live poultry. Results The live poultry feeding rate and live poultry purchasing rate in residents in Beijing in the past year were 5.3%(95%CI:4.8%-5.8%) and 6.0% (95%CI: 5.5%-6.5%) respectively. Logistic regression analysis indicated that lower educational level of primary school and below, (OR=1.82, 95%CI:1.22-2.72);being farmer (OR=2.49, 95%CI:1.89-3.29) or being unemployed (OR=1.65, 95%CI:1.08-2.52);being non local resident (OR=1.54, 95%CI:1.10-2.16);living in suburban area (OR=2.36, 95%CI:1.77-3.16);having one child (OR=1.76, 95%CI: 1.42-2.17) or ≥2 children (OR=2.15, 95%CI: 1.43-3.22) in the family were the risk factors associated with feeding poultry compared with higher educational level of college and above, being employed, being local resident, living in urban area and having no child. And being farmer (OR=1.61, 95%CI:1.27-2.02);being non local resident (OR=1.76, 95%CI:1.31-2.35);living in suburban area (OR=2.05, 95%CI:1.61-2.61);having one child (OR=1.24, 95%CI:1.02-1.52) or ≥2 children (OR=1.78, 95%CI: 1.21-2.63) were the risk factors for purchasing live poultry. Conclusion Some residents living in Beijing still have exposure to live poultry, and targeted measures should be taken to reduce the exposure to poultry.
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Objective To investigate the changes and clinical significance of peripheral blood T lymphocyte subsets and cytokines in influenza A (H7N9) virus infection patients.Methods Twenty-three patients with H7N9 virus infection who received treatment at the First Affiliated Hospital of Soochow University from April 2013 to April 2015 were enrolled as case group.Twenty healthy subjects in the outpatient clinic during the same period were selected as control group.The percentages of T lymphocyte subsets in the peripheral blood including CD3+CD4+ T cells, CD3+CD8+ T cells, regulatory T lymphocytes (Treg), Th17, CD3+CD8-interferon (IFN)-γ+ (Th1) cells and CD3+CD8-IL-4+ (Th2) cells were detected by flow cytometry.The changes of plasma cytokines including interleukin (IL)-8, IL-18, interferon-inducible protein (IP)-10, macrophage inflammatory protein (MIP)-1b were quantified by Bio-Plex Pro human cytokine Group Ⅰ 27-plex panel and Group Ⅱ 21-plex panel.The normality test was performed by Kolmogorov-Smirnov test.Two independent samples t test were used to compare the two groups.Results The percentages of CD3+CD4+ and CD3+CD8+ T cells before treatment in case group were significantly lower than control group ([27.90±10.19]% vs [38.75±6.78]%, t=-2.726, P=0.012;[14.82±7.72]% vs [22.79±6.12]%, t=-2.556, P=0.018), while the percentages of Th17 and Th2 before treatment in case group were significantly higher than control group ([2.64±1.40]% vs [0.29±0.21]%, t=4.668, P0.05).Before treatment, levels of IL-8, IL-18, IP-10 and MIP-1b of case group were significantly higher than those in control group (IL-8: [23.19±14.35] vs [12.78±6.76] ng/L, t=2.277, P=0.035;IL-18:[230.55±230.18] vs [72.80±27.91] ng/L, t=2.348, P=0.036;IP-10:[28 870.55±41 815.22] vs [1 356.13±1 093.10] ng/L, t=2.371, P=0.035;MIP-1b: [197.74±119.87] vs [118.51±41.86] ng/L, t=2.198, P=0.043).Conclusions Patients with H7N9 virus infection exhibit an imbalance of T lymphocyte subsets.It is very important to monitor the changes of T lymphocyte subsets in those patients for clinical prognosis.A storm of cytokines could exist during H7N9 virus infection, which may be the main reason for multiple organ failure.
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To analyze the epidemiological characteristics of human infection with avian influenza A(H7N9) virus from 2013 to 2016 in Xiaoshan,China,we collected the epidemiological data of human A(H7N9) cases as well as the results of environmental monitoring and analyzed it by case study,descriptive epidemiological method,and statistical analysis.Results showed that a total of 22 cases were confirmed,including 12 deaths.All the cases occurred in winter and spring,and most of them had been exposed to live poultry,and with the underlying condition of chronic diseases.Chi-square test showed that the ratio of cases with chronic diseases in death group was higher (P=0.01).The environmental monitoring result showed there were distinctive seasonal differences of positive rate with peaks in winter and spring and nadirs in autumn and summer.Positive rates for the samples from external environmental monitoring were consistent with the distribution of the case onset.Due to rise of environmental monitoring positive rate,we should be alert to the occurrence of new cases,especially in rural areas where live poultry fairs still exist and among people with occupational exposure.We should further improve ability to prevent and control this disease.
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Objective@#To prepare strains of influenza A (H7N9) pseudovirus derived from different districts of China for vaccine efficacy evaluation.@*Methods@#Phylogenetic tree was built based on hemagglutinin (HA) amino acid sequence analyses from 29 influenza A (H7N9) virus strains and 6 influenza A (H7N9) virus strains with HA determinants variation were selected. 293FT cells were co-transfected with plasmid pNL4-3-Luc.R-E-, pVRC-HA and pVRC-NA with codon-optimized hemagglutinin (HA) and neuraminidase (NA) derived from the six influenza A (H7N9) virus strains, respectively. Transmission electron microscopy assay and Western blot analysis were performed to demonstrate morphology and specificity of these particles, luciferase activity assay and hemagglutinin titers detection were used to determine their infectivity and hemagglutinin activity. And finally, pseudovirus-based neutralization assays were evaluated with HA immunized mice serum.@*Results@#Six influenza A (H7N9) peseudovirus particles derived from different districts of China were selected and prepared. All of the particles bearing HA and NA were characterized with classic influenza virus morphology, with TCID50 titer ranged from 104TCID50/50 μl to 105TCID50/50 μl and with hemagglutinin activity ranged from 64 to 512. Neutralization efficacies on influenza A/Shanghai/1/2013(H7N9) HA vaccine serum against 100TCID50 dose of these pseudovirus particles indicated their potential application in the vaccine cross-protective evaluation in future.@*Conclusions@#Six influenza A (H7N9) pseudovirus derived from different districts of China with potential antigenic variation on HA were constructed successfully, established foundation for their further application in vaccine cross-reactive efficacy evaluation.
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Objective Influenza A(H7N9) virus causes a relatively high mortality in humans and therefore it is of great sig-nificance to know its prevalence in China .This article aimed to study the genetic characteristics and evolution of the hemagglutinin (HA) gene of the influenza A(H7N9) virus prevailing in China between 2013 and 2017. Methods We downloaded the HA se-quences of the influenza A ( H7N9) virus prevailing in China between 2013 and 2017 from The Global Initiative on Sharing All Influen-za Data and National Center for Biotechnology Information .Using the bioinformatics software , we analyzed the homology , molecular characteristics , phyletic evolution , and selective pressure of the HA gene. Results The homology of the HA gene of the influenza A ( H7N9) virus and the reference strain was decreasing each year from 2013 to 2017, 99.0%-99.9%in 2013, 98.7%-99.5%in 2014, 98.4%-99.6%in 2015, 76.8%-99.4%in 2016, and 69.9%-98.2%in 2017.Compared with the reference strain , the HA gene of the influ-enza A(H7N9) virus underwent variations in 21 antigenic sites.The variation of N285D was the highest (23%) in 2015 and that of R148K increased yearly,reaching 65%in 2016 and 78.5% in 2017. Phylogenetic analysis showed a concentrative distribution of the influenza A ( H7N9) virus strains on the phylogenetic tree in the same year from 2013 to 2017.Amino acid substitution of T 140A was observed in most of the influenza A ( H7N9) virus strains from Guang-dong in 2013, and the widest distribution of the virus strains was found in 2014.Positive selective pressure site 65 was obtained in the sequence of 2015 using the FEL and IFEL models, but not in the strains of 2016 or 2017. Conclusion Influenza A(H7N9) virus constantly undergoes variation , which has increased the difficulty in its prevention and control .More importance should be attached to observation of the virus and response to its adaptive mutations .
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Objective Influenza A(H7N9) virus causes a relatively high mortality in humans and therefore it is of great sig-nificance to know its prevalence in China .This article aimed to study the genetic characteristics and evolution of the hemagglutinin (HA) gene of the influenza A(H7N9) virus prevailing in China between 2013 and 2017. Methods We downloaded the HA se-quences of the influenza A ( H7N9) virus prevailing in China between 2013 and 2017 from The Global Initiative on Sharing All Influen-za Data and National Center for Biotechnology Information .Using the bioinformatics software , we analyzed the homology , molecular characteristics , phyletic evolution , and selective pressure of the HA gene. Results The homology of the HA gene of the influenza A ( H7N9) virus and the reference strain was decreasing each year from 2013 to 2017, 99.0%-99.9%in 2013, 98.7%-99.5%in 2014, 98.4%-99.6%in 2015, 76.8%-99.4%in 2016, and 69.9%-98.2%in 2017.Compared with the reference strain , the HA gene of the influ-enza A(H7N9) virus underwent variations in 21 antigenic sites.The variation of N285D was the highest (23%) in 2015 and that of R148K increased yearly,reaching 65%in 2016 and 78.5% in 2017. Phylogenetic analysis showed a concentrative distribution of the influenza A ( H7N9) virus strains on the phylogenetic tree in the same year from 2013 to 2017.Amino acid substitution of T 140A was observed in most of the influenza A ( H7N9) virus strains from Guang-dong in 2013, and the widest distribution of the virus strains was found in 2014.Positive selective pressure site 65 was obtained in the sequence of 2015 using the FEL and IFEL models, but not in the strains of 2016 or 2017. Conclusion Influenza A(H7N9) virus constantly undergoes variation , which has increased the difficulty in its prevention and control .More importance should be attached to observation of the virus and response to its adaptive mutations .
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We analyzed genetic evolution characteristics of avian influenza A (H7N9) virus isolated in Zhaoqing,China,2014-2016.Nucleic acid were extracted and sequenced from 17 samples of H7N9 positive cases in Zhaoqing.Genetic characteristics of homology and important amino acid sites were analyzed by using BioEdit5.0 and MEGA6.0.The evolutionary trees were constructed by Neighbor-Joining and the referenced sequences were downloaded from GenBank,Eight nucleic acid fragments from 7 strains of H7N9 viruses were successfully generated.The highest homology was found in HA gene with A/chicken/Dongguan/695/2014(H7N9),and NA gene with A/chicken/Dongguan/1075/2014(H7N9).The internal genes were high homology with avian H7N9 and H9N2 virus from Dongguan and Shenzhen in Guangdong,China.The HA and NA genes were directly evolved in the Pearl River Delta evolution branch with the H7N9 sequences from the cities of Dongguan,Guangzhou and Shenzhen,while the sequences from the provinces of Anhui,Zhejiang,and Jiangsu were in the Yangtze River Delta evolution branch.There were 2 alkaline amino acids in cleavage site of HA,2 mutations (G186V and Q226L) in the crucial sites related with the receptor of HA protein,1 mutation (E627K) in PB2 protein,and 1 drug resistance mutation (S31N) in M2 protein.And no evidence of neuraminidase resistance in NA protein was found.In conclusion,the H7N9 virus for human infection in Zhaoqing may originate from avian H7N9 and H9N2 viruses,which circulated in the Pearl River Delta region of Guangdong from 2013 to 2014.The mutations of G186V,Q226L and E627 K might be related with high susceptibility to human beings.