H7N9 is a novel avian virus recently first reported from Shanghai in China. Very recently an isolate from Taiwan was also reported . H7N9 is able to infect humans and has caused many fatal cases [2, 3]. Determining the origin and evolution of these disease-causing viruses is important for surveillance and prevention of the influenza epidemics. With more and more reported pathogenic H7N9 isolates reported, it is important to reexamine whether these disease-causing H7N9 isolates all came from the same common ancestor and whether they have undergone further reassortments.