The limited number of available nucleotide and protein sequence data from the recent H7N9 cases in China impeded investigation and characterization of the outbreak

Dear Editor,Nucleotide and protein sequences of isolates collected from infected populations can be useful for determining the threats,such as host adaptation,which are associated with the emergence of new lineages.March 2013 saw the first reports of a new H7N9 lineage in Shanghai,China that saw a gradual increase in the number of cases;but,by 17th May 2013,four Chinese provinces had ended their emergency response to H7N9 bird flu.However,despite detailed reports on human cases,the publicly available sequences from collected isolates were relatively few.By analyzing the data at this time we show that limited insight can be obtained from a relatively small dataset and,in particular,more avian isolates are necessary to consider host adaption.With reports of new H7N9 cases in South China our findings are relevant to establishing effective monitoring and determining the risk associated with these new events.