Comparison of pathogenicity and transmissibility of the novel avian-origin human A(H7N9) influenza virus and other strains in ferrets

Objective the novel avian-origin H7N9 subtype influenza virus caused outbreak of human infections in China since March 2013.The aim of this study was to better understand the pathogenicity and transmissibility of the H7N9 influenza virus in ferrets to verify whether this new emerging infectious H7N9 virus can infect humans,and to compare the transmission ability of this virus with that of other influenza virus subtypes in ferrets.Methods A/Anhui/1/2013(H7N9) virus was administered by intranasal instillation to groups of ferrets.Clinical signs,virus shedding from respiratory tract and pathological changes were recorded.Meanwhile,the replication ability,virulence and pathogenicity were investigated in ferret models and compared with those of 2009 pandemic H1N1 and H5N1 influenza viruses.Results In the ferret models,based on the clinical signs,mortality,virus dissemination,and pathological analysis,the H7N9 influenza virus was found to be less pathogenic than the H5N1 virus but was comparable with the 2009 pandemic H1N1 virus.The H7N9virus could replicate in the upper and lower respiratory tract,heart,liver,and olfactory bulb.It is worth noting that the H7N9 virus exhibited low level of transmission between ferrets via respiratory droplets.There were four mutations in the virus isolated from the contact ferrets.Conclusions These data indicate that H7N9 subtype influenza virus is transmissible among ferrets,and the pathogenicity of avian-origin H7N9 subtype influenza virus is lower than that of H5N1 subtype influenza virus between ferrets,and is comparable to that of H1N1 influenza virus.