| Objective:Avian influenza A(H7N9)virus poses a great threat to the human health for its ability to cross the species barrier and infect humans.We aimed to explore the distribution of environmental H7N9 influenza virus and trace the origin of the human H7N9 virus in Fujian Province,to establish an early warning mechanism and provide a scientific basis for prevention and control of human infection with H7N9 virus.Methods:The environmental Avian Influenza Virus samples from six cities in Fujian Province were collected through the Fujian Influenza Surveillance System during the period from 2013 to Sep 2018.The epidemiological characteristics of avian influenza virus in environmet were analyzed and to explore if there has a correlation between the H7 subtype virus and human infection with H7N9 in Fujian Province.The sequences of H7N9 virus were spliced and aligned through bioinformatics software.The genetic sequences from Yangtze River Delta and the Pearl River Delta were retrieved from online databases.Chi-square tests were used to compare the viral subtype positive rates.Phylogenetic tree analysis and molecular analysis were conducted to seek the transmission route of the human infection and to map out the evolutionary routes of H7N9 viruses in Fujian.Results:1.Epidemiological characteristics of avian influenza virus in Fujian Province(1)From 2013 to Sep 2018,a total of 5548 environmental specimens were collected from Fujian Province,of which 1815 were positive for avian influenza virus,and the positive rate was 32.71%.The highest positive rate was 71.59%in Jan 2017 and the lowest was 0%in May 2013.The highest positive rate of influenza avian virus was in the first and fourth quarters and the lowest rate was in the second and third quarters.There was a statistically significant difference in the positive rate of avian influenza virus among the four quarters(χ2=67.299,P<0.001).(2)There was a statistically significant difference in the positive rate of avian influenza virus in different surveillance cities(χ~2=613.903,P<0.001).The highest positive rate was 56.10%in Xianmen and the lowest rate was 5.01%in Zhangzhou.(3)The positive rate was 40.43%,12.03%,6.09%and 0.36%in live poultry market,poultry slaughtering and processing plant,poultry household and the poultry farm,respectfully.There was a statistically significant difference in the positive rate of avian influenza virus in different survellance sites(χ~2=537.263,P<0.001).(4)In different types of specimens,the highest positive avian influenza virus rate was 39.05%of cleaning poultry sewage,followed by 36.36%of poultry chopping board,cage surface was 33.05%,poultry drinking water was 32.26%and poultry feces was29.32%.The positive rates of avian influenza virus among different types of specimens were statistically significant(χ~2=28.836,P<0.001).The positive rate of cleaning poultry sewage and poultry chopping board specimens were significantly higher than the poultry feces(P<0.05).2.The number of H7 subtypes in environment was in accordance with the human infected H7N9 cases in Fujian Province in time distribution(Spearman=0.858,P<0.001).3.The virus samples from the patient and birds shared high homology(96.27%-100%)in all eight gene segments.The genetic evolution of HA and NA genes were relatively stable.The homology of eight genes were statistically significant(F=333.98,P<0.001).4.Phylogenetic trees showed that the H7N9 virus of HA and NA genes in Fujian Province were branched according to the different years.Moreover,the H7N9 virus isolated from the external environment and the human were closely related to each other,and were classified into the same genetic clade in the same year.The H7N9 strain isolated from Fujian Province was mainly origned from the Yangtze River Delta and the Pearl River Delta regions.Conclusions:In Fujian Province,the avian influenza virus might be emerged in the surrounding environments especially in the live ploutry markets.According to the epidemiological characteristics of avian influenza virus,we should take targeted measures to provide a scientific basis for prevention and control of H7N9 outbreaks.The H7N9 virus can be carried by birds and therefore be spread in different Province.And the patients with H7N9 infection were most likely to be infected the virus from contaminated poultry environment.The H7N9 avian influenza virus gene isolated from Fujian Province is relatively stable which is beneficial to carry out the vaccination in birds. |
