Study On The Diversity Of Avian Influenza Viruses In Poultry And Wild Birds

The influenza virus is a negative-strand RNA virus whose genome consists of 8fragments and is widely infected by birds and mammals.Some avian influenza viruses(AIV),such as H5N1 along with H7N9,can transmit diseases to humans through cross-host transmission,causing diseases or deaths in the population,which is seriously threatening the safety of global public health.Previous studies on the diversity of avian influenza viruses have focused on a small range of countries or regions,and studies on the diversity of avian influenza viruses around the world are rare.In this study,we systematically collected a data set of AIV internal genes from 75 regions worldwide over 11 years,and constructed a database of internal gene sequences of the avian influenza virus.We mapped the distribution of sampling sites and calculate the diversity of AIV internal genes in poultry and wild birds.By fitting regression analysis of diversity and latitude gradient,it was found that the genetic diversity of the internal genes of AIV increased with the increase of latitude gradient in wild birds.Wild birds have long been thought to serve as the natural reservoirs of influenza viruses,and thus it is expected that wild birds harbor higher viral diversity than poultry.Yet,this hypothesis has not been formally tested.Here,we compared the genetic diversity of wild bird AIV with that of poultry AIV.We find the genetic diversity of the internal genes of AIV in wild birds is not significantly higher than that in poultry.To avoid sampling errors,we also examine the number of HA and NA subtypes in poultry and wild birds and the correlation between the sampling areas and genetic diversity.These factors were found to have no effect on the size of genetic diversity.We calculated the rate of transmission of AIV between poultry and wild birds.It was found that there are two ways to spread the AIV,either from wild birds to poultry or from poultry to wild birds.We propose that the unexpected diversity patterns of AIV internal genes could be explained by the synchronized global sweep of AIV internal genes occurring in the late 1800 s and frequent AIV transmission between wild birds and poultry.We systematically collected a data set of AIV external genes from 107 regions worldwide over 11 years to compare the diversity of AIV external genes in poultry and wild birds.There is no general pattern of genetic diversity of AIV in poultry and wild birds for external genes.However,the synchronized global sweep of AIV genes occurring in the late 1800 s did not involve external genes.This study analyzed the diversity of AIV gene fragments in poultry and wild birdsworldwide,expanded our understanding of AIV genetic diversity,and had important significance for the comprehensive understanding of the evolution of influenza virus.