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The avian influenza A (H7N9) virus is a zoonotic virus that is closely associated with live poultry markets. It has caused infections in humans in China since 2013. Five waves of the H7N9 influenza epidemic occurred in China between March 2013 and September 2017. H7N9 with low-pathogenicity dominated in the first four waves, whereas highly pathogenic H7N9 influenza emerged in poultry and spread to humans during the fifth wave, causing wide concern. Specialists and officials from China and other countries responded quickly, controlled the epidemic well thus far, and characterized the virus by using new technologies and surveillance tools that were made possible by their preparedness efforts. Here, we review the characteristics of the H7N9 viruses that were identified while controlling the spread of the disease. It was summarized and discussed from the perspectives of molecular epidemiology, clinical features, virulence and pathogenesis, receptor binding, T-cell responses, monoclonal antibody development, vaccine development, and disease burden. These data provide tools for minimizing the future threat of H7N9 and other emerging and re-emerging viruses, such as SARS-CoV-2.
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Animals , Humans , COVID-19 , China/epidemiology , Influenza A Virus, H7N9 Subtype , Influenza in Birds/epidemiology , Influenza, Human/prevention & control , Poultry , SARS-CoV-2ABSTRACT
Background METTL3 (methyltransferase like 3) and FTO (fat mass and obesity-associated protein) are criticalfor establishing and regulating the m6A (N6-methyladenosine) modification, but very little is known about thefunction of m6A in the immune system or its role in interactions within the host immune system.Methods Western blotting experiment was used to check the expression of the host proteins related to m6Amodification after H7N9 influenza virus infection. Immunofluorescence experiment was used to identifywhether the subcellular localization of related proteins. Moreover, we knocked down and over expressendogenous METTL3 or FTO in A549 cells, and then infected the cells with H7N9 to test whethermethyltransferases or demethylases affect H7N9 replication.Result We confirmed that the expression pattern of m6A proteins was altered during H7N9 infection. METTL3and FTO were located in the nucleus, and YTHDF3 was located in the cytoplasm. Furthermore, our resultsdemonstrate that downregulation of METTL3 or FTO expression in A549 cells severely impairs viral proteinexpression and H7N9 infection.Conclusions METTL3 and FTO are critical for H7N9 replication which may represent a new mechanism for thecontrol of H7N9 replication and host-pathogen interactions.
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H7N9 avian influenza is a new subtype of avian influenza, first found in the Yangtze River Delta at the end of February 2013. H7N9 avian influenza, infection in human is transmitted through the respiratory airway, causing acute respiratory infectious disease. Due to the species barrier, H7N9 avian influenza virus only infect human via birds occasionally under very specific circumstances, and at present, there is no exact evidence of H7N9 avian influenza virus transmission between humans. However, H7N9 avian influenza remains a continuous public health threat. So far, China has had six outbreaks of H7N9 avian influenza. A total of 1567 cases of H7N9 influenza virus infection have been reported to WHO, including 615 deaths. When H7N9 avian influenza virus infects the human body, their primary target of infection is the respiratory mucosal epithelial cells. Therefore, the respiratory epithelium plays a key role in the process of virus transmission and infection. Hence, the main purpose of this review is to collate the current understanding of immune responses and their corresponding molecular mechanisms of mucosal damage caused by H7N9 avian influenza infection, and how it contributes to cross species human infection.
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[Objective] To analyze and judge the possibility of early control in Shanghai if COVID-19 begins in Shanghai. [Methods] Compare the process of early control of H7N9 avian influenza in Shanghai in 2013 and Wuhan COVID-19 in 2019. The early incidence data of Korean COVID-19 was simulated and analyzed to predict whether the medical resources needed in Shanghai were available. [Results] (1) It would take 22 days from the first case to the government's emergency response in terms of Shanghai. (2) It is estimated that there would be 602-763 patients with cumulative onset and onset after incubation period. (3) At least 500 beds of infectious diseases can be allocated in Shanghai in case of emergency. Through adding beds and resources reallocation in the whole city, patients can be fully admitted and treated. [Conclusion] If COVID-19 epidemic occurs in Shanghai, early control is possible.
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Objective To analyze and estimate the possibility of early control in Shanghai if COVID-19 had begun in Shanghai. Methods Comparison was made in the processes of early control between H7N9 avian influenza in Shanghai in 2013 and COVID-19 in Wuhan in 2019.The early incidence data of Korean COVID-19 was simulated and analyzed to predict whether the medical resources needed in Shanghai were available. Results If it had occurred in Shanghai, it would have taken 22 days from the first case to the government′s emergency response.It was estimated that there would have been 602-763 patients with cumulative onset and onset after incubation period.At least 500 beds of infectious diseases could have been allocated in Shanghai in case of emergency.Through adding beds and resources reallocation in the whole city, patients could have been fully admitted and treated. Conclusion If COVID-19 epidemic had occurred in Shanghai, it′s early control would have been possible though there might have difficulties.
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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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Objective To analyze the epidemiological characteristics of human infection with H7N9 avian influenza in Guilin in recent years and to provide on-site data and data support for scientific pre-vention and control of the epidemic of H7N9 avian influenza infection. Methods A descriptive epidemio-logical method was used to collect the data about human infection with H7N9 avian influenza form three as-pects, which were human infection cases in 2017, environmental monitoring for H7N9 avian influenza virus and sentinel surveillance of influenza-like cases. The epidemiological characteristics of human infection with H7N9 avian influenza in Guilin in 2017 were analyzed. Chi-square test was used to compare the positive rates of H7N9 avian influenza virus in environmental specimens. Results A total of six cases of confirmed human H7N9 infection including three deaths were reported in Guilin city in 2017. These cases were from five counties and districts and all occurred in winter and spring. The patients were middle-aged and old men. Most of them were farmers and had a clear history of poultry exposure before the onset of infection. No human H7N9 infection was reported in close contacts or in influenza-like cases. Conclusions H7N9 avian influen-za infection in Guilin was characterized by high sporadicity, high incidence in winter and spring, and pre-dominantly middle-aged and elderly men. Avian exposure history was a high risk factor for human infection with H7N9 avian influenza virus. All of the studied cases were severe cases. No human-to-human transmis-sion was reported. Farmers, having a history of poultry slaughter, and underlying diseases were potential risks causing death. Live poultry markets were the main sources of infection, hence closing market could re-duce the detection rate of H7N9 avian influenza virus. Strengthen the management of live poultry market and poultry environmental monitoring, closing live poultry markets when viral detection was positive, and suspen-ding live poultry trading were effective measures to control the epidemic of H7N9 avian influenza infection and prevent transmission.
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Objective To develop an enzyme-linked lectin assay ( ELLA ) for measuring neuraminidase inhibition (NI) antibody titers in subjects vaccinated with H7N9 influenza vaccine. Methods Neuraminidase substrate, the dilution and incubation time of enzyme-labeled antibody, the concentration of influenza antigen for coating and pH value of the dilution buffer were optimized. Based on that, ELLA was established and used to detect anti-influenza neuraminidase antibody titers in serum samples of 34 subjects before and after vaccination with H7N9 influenza vaccine. Results The optimal neuraminidase substrate was fetuin at a coating concentration of 7. 5 μg/ml. The optimal dilution of enzyme-labeled antibody was 1 : 500. The virus strain of influenza H7N9 vaccine was used as antigen at a concentrations of 4. 5lgCCID50/ml in solution with a pH of 6. 5. Influenza-specific NI titers detected after immunization with vaccine were significantly higher than those before vaccination (P<0. 001). In the 34 subjects receiving H7N9 vaccine, the seroconversion rate of NI antibody was 47％ (≥40 in NI titer ), which was lower than that of HI antibody (P<0. 05). Conclusions An ELLA with natural substrate for measurement of anti-in-fluenza NI antibody was developed. It is simple and practical and might be used in the establishment of im-mune evaluation system for influenza vaccines and NI antibody.
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Objective To explore the predictive value of neutrophil-to-lymphocyte ratio on the prognosis of H7N9 avian influenza.Methods A retrospective analysis was conducted on 28 H7N9 avian influenza patients (treatment group) at the First Affiliated Hospital of Soochow University from April 2013 to January 2016.Thirty healthy physical examiners in the same period were enrolled as the healthy control group.The 28 patients were followed up for half a year and divided into the improvement group (18 cases) and the death group (10 cases) according to the clinical prognosis.Inflammatory indicators including white blood cells (WBC),neutrophil (N),lymphocyte (L),monocytes (M),platelet (PLT),creatine kinase (CK),lactate dehydrogenase (LDH),high sensitive C reactive protein were collected at day 1,day 3 and week 1 of admission.Calculation of neutrophil-to-lymphocyte ratio (NLR),platelet-to-lymphocyte ratio (PLR),lymphocyte-to-monocyte ratio (LMR),△NLR3 (day 3 of admission NLR-on day 1 of admission NLR),△NLR7 (week 1 of admission NLR-day 3 of admission NLR) and so on calculating △PLR3,△PLR7,△LMR3,△LMR7.Differences of the above indicators between the improvement group and death group were compared.The measurement data with normal distribution were tested by t-test of two independent samples,and the count data with non-normal distribution were tested by Mann-Whitney U-test.Univariate and multivariate logistic regression analysis to explore the prognostic factors and the working characteristic curve of subjects was used to evaluate the predictive value of inflammatory response indexes for H7N9 avian influenza death.Results In the treatment group,the baseline WBC,L,N,PLT,the proportion of lymphocytes,neutrophils,monocytes,and NLR,PLR,and LMR were all statistically different compared with the healthy control group (all P ＜0.01).After treatment,day 3 NLR,△NLR3 in improvement group were both significantly decreased to 10.93 (15.71)and0.87 (-15.63),respectively when compared with death group (17.62[23.63] and 7.42[22.68],respectively) (Z =-2.16 and-2.014,respectively,both P＜0.05).Day 7 NLR,△NLR7 in improved group were 6.51 (13.23) and-0.37 (-12.38),respectively,which were both lower than those of death group (27.90 [25.64] and 11.54 [-26.22]) with statistically significant differences (Z =-2.444 and -2.111,respectively,both P ＜ 0.05).Multivariate logistic regression analysis indicates that △NLR3 is the main factor that affects the prognosis of the H7N9 infection (odds ratio [OR] =1.153,95％ confidence interval [CI]:1.052-1.263,P =0.002).Reciver operating characteristic curve analysis showed that the area under the curve was 0.733 (95 ％ CI:0.532-0.935,P =0.044).Based on the principle of Youden index,the cutoff value of △NLR3 to predict the death risk of H7N9 avian influenza was 5.453 with sensitivity of 0.700 and the specificity of 0.722.The mortality was higher when △NLR3 was higher than 5.453.Conclusions Dynamic monitoring NLR,especially △NLR3 may reflect the condition and prognosis of H7N9 infection,which is an independent predictor of death.
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Objective@#To investigate the best amount of TPCK trypsin in Madin Darby canine kidney (MDCK) cell suspension for the culture of H7N9 avian influenza virus.@*Methods@#Different concentrations of TPCK trypsin were added during the periods of cell growth and virus production. Their effects on cell growth, viability, glucose and lactate metabolism, and hemagglutination titer were monitored every 12 h. Inter-batch differences were analyzed. The amount of trypsin added in the cell growth phase was 0, 1 μg/ml, 2 μg/ml, 4 μg/ml, 6 μg/ml, 8 μg/ml, 10 μg/ml and 15 μg/ml. The amount of trypsin added during the virus production period was 0, 0.5 μg/ml, 1 μg/ml, 1.5 μg/ml, 2 μg/ml and 2.5 μg/ml. When the hemagglutination titers were same, the adding amount was further optimized at different multiplicity of infection (MOI) of 0.001, 0.005, 0.025 and 0.05.@*Results@#No significant linear effects of TPCK trypsin concentration on cell number, viability, and glucose and lactate metabolism were observed. No toxicity to cell growth was observed when TPCK trypsin concentration reached 15 μg/ml. After the inoculation of H7N9 avian influenza virus, the hemagglutination titers in the 1 μg/ml, 1.5 μg/ml, 2 μg/ml and 2.5 μg/ml TPCK trypsin groups reached the peaks at 48 h, which were 1∶26.5. At 60 h, the hemagglutination titers of the latter two groups decreased faster than those of the former two groups. When the MOI was 0.005, the hemagglutination titer of the 1.5 μg/ml group at 48 h was 26.5 higher than 26 in the 1 μg/ml group under the same condition. There were differences between different batches of TPCK trypsin.@*Conclusions@#Adding 1 μg/ml and 1.5 μg/ml of trypsin could better promote the proliferation of H7N9 avian influenza virus, and 1.5 μg/ml of trypsin had a wider range of MOI applicability.
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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 develop the chimeric antibodies against neuraminidase (NA) of H7N9 and to identify their biological activity and function.@*Methods@#The genes of variable regions of the light chain (VL) and heavy chain (VH) obtained by mouse hybridoma technology were cloned respectively into the expression VH and VL vectors bearing human-derived Cγ1, and Cκ1 and co-transfected into 293T cells. The chimeric antibodies were purified and their functions were investigated.@*Results@#Two chimeric antibodies, 1E2 and 3E3 against neuraminidase (NA) of H7N9 were obtained. Both antibodies recognized similar antigenic epitopes. MAb 1E2 and 3E3 could prevent the infectivity with H7N9 and H11N9 virus and reduce their size of viral plaque.@*Conclusions@#The chimeric antibodies specific for N9 could prevent the infection of N9 subtype influenza virus as well as the NAI-resistant mutants and could be a potential immunotherapy approach for H7N9 treatment.
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Objective @#To evaluate the immune effects of inactivated H7N9 influenza vaccine.@*Methods @#We searched several common databases（The Cochrane Library,PubMed,China Biology Medicine disc,China National Knowledge Infrastructure,etc.）for research articles about immune effects of H7N9 influenza vaccine published from the time the database built to July 10th of 2018,using H7N9 and vaccine as keywords. After screening the articles according to the inclusion and exclusion criteria,we assessed the quality of the studies and then employed seroconversion rate（SCR）as an outcome indicator to analyze the immune effects of different doses and adjuvants.@*Results @#We recruited 5 articles on inactivated H7N9 influenza vaccine from 1 679 articles. The sample size was 2 579. The results of the meta-analysis showed that the rate difference（RD）values of SCR in each dose group after the first dose ranged from 1% to 10%,which indicated a poor protective effect;after the second dose of immunization,the RD values of SCR in the vaccines without adjuvants ranged from 13% to 19%,which was not effective enough;the RD values of SCR in the vaccines with adjuvants ranged from 62% to 69%,which met the licensing criteria for influenza vaccine;better results could be achieved when immunized with two doses of vaccines with adjuvants（ RR=1.19,95%CI：1.02-1.39）;vaccines with AS03 or MF59 at the lowest dose of 3.75 μg had the same immune effects as ones at a dose of 15 μg;vaccines with AS03（RD=89%,95%CI：85%-93%）were superior to those with MF59（RD=42%,95%CI：9%- 75%）.@*Conclusion @#Inactivated H7N9 influenza vaccines could achieve good immune effects when inoculated two doses with adjuvants,and the minimum effective dose was 3.75 μg.
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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 study the willingness and influence factors related to "centralized slaughtering,fresh poultry listing and marketing" strategy,among the household chefs,and provide reference for government to adjust and optimize the strategy on avian influenza prevention.Methods According to the geographical characteristics and regional functions,6'monitoring stations' were selected from 12 residential districts of Guangzhou,respectively.Another 21 meat markets which selling live poultry,were selected in each station and 5 household chefs of each market were invited to attend a face to face interview.Basic information,personal cognitive,willingness and influencing factors to the policy were under study.Univariate and multivariate logistic regression methods were used.Results A total of 664 household chefs underwent the survey and results showed that the rate of support to the "centralized slaughtering,fresh poultry listing and marketing" strategy was 44.6％ (296/664).Results from the multi-factor logistic regression showed that those household chefs who were males (OR=1.618,95％ CI:1.156-2.264,P=0.005),having received higher education (OR=1.814,95％ CI:1.296-2.539,P=0.001),or believing that the existence of live poultry stalls was related to the transmission of avian influenza (OR=1.918,95％CI:1.341-2.743,P＜0.001) were factors at higher risk.These household chefs also intended to avoid the use of live poultry stalls (OR =1.666,95％CI:1.203-2.309,P=0.002) and accept the "centralized slaughtering,fresh poultry listing and marketing" strategy.Conclusion Detailed study on this subject and,setting up pilot project in some areas as well as prioritizing the education programs for household chefs seemed helpful to the implementation of the'freezing-fresh poultry'policy.
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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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In 2013, two episodes of influenza emerged in China and caused worldwide concern. A new H7N9 avian influenza virus (AIV) first appeared in China on February 19, 2013. By August 31, 2013, the virus had spread to ten provinces and two metropolitan cities. Of 134 patients with H7N9 influenza, 45 died. From then on, epidemics emerged sporadically in China and resulted in several victims. On November 30, 2013, a 73-year-old woman presented with an influenza-like illness. She developed multiple organ failure and died 9 d after the onset of disease. A novel reassortant AIV, H10N8, was isolated from a tracheal aspirate specimen that was obtained from the patient 7 d after onset. This case was the first human case of influenza A subtype H10N8. On 4 February, 2014, another death due to H10N8 avian influenza was reported in Jiangxi Province, China.
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Aged , Female , Humans , China , Epidemiology , Influenza A Virus, H10N8 Subtype , Classification , Influenza A Virus, H7N9 Subtype , Classification , Influenza A Virus, H9N2 Subtype , Classification , Influenza, Human , Epidemiology , Virology , Phylogeny , Reassortant Viruses , ClassificationABSTRACT
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 analyze the distribution and the molecular biological characteristics of variant subtypes (H5, H7 and H9) of avian influenza virus (AIV) in the live poultry related external environment of Quanzhou form 2014 to 2017, and provide regional references for the prevention, control and early-warning of human infections.@*Methods@#Samples from monitoring sites of live poultry were collected in Quanzhou from 2014 to 2017. Influenza A and variant subtypes of AIV (H5, H7 and H9) were detected by real time RT-PCR, and the detection results were further analyzed statistically. Furthermore, the HA and NA genes of four representative H7N9 strains were sequenced, and the results were further analyzed with DNAstar and MEGA7.0.@*Results@#Among the samples from external environment, the positive rate of nucleic acid of influenza A was 29.04% (377/1 289), of which the positive rates of H5, H7 and H9 subtypes were 3.80%, 13.34% and 12.02%, respectively. The positive rate of H7N9 was higher than those of the other subtypes in all monitored years, of which the highest rate was found in 2017 (21.88%). As to the different types of samples, chopping board possessed the highest positive rate of influenza A (65.4%), followed by waste water (59.3%) and drinking water for the poultry (29.6%). Among the different monitoring sites, the positive rate of poultry farm is 6.94%, far lower than that in the open air (61.7%) and the live poultry trading market (52.8%). Sequencing of the HA and NA genes of four strains of H7N9 showed that the strains from external environment and the strains from H7N9 patients belonged to Pearl River Delta and Yangtze River Delta lineage, respectively. The cleavage sites of HA proteins of these four strains were all PKGR/G without highly pathogenic mutation. Meanwhile, they were low pathogenic H7N9 without oseltamivir resistant mutation (R292 K in NA), while they all possessed the E627 K mutation in the PB2 genes associated with virulence.@*Conclusions@#H7N9 AIV existed in the live poultry related external environment of Quanzhou, especially the farmers’ and the live poultry trading market, so that more persistent surveillance could be needed in the future.