Neurogenesis in the adult CNS is regulated by the neural stem/progenitor cells residing in the subventricular zone (SVZ) of the lateral ventricles, and subgranular zone (SGZ) of the hippocampus [18,19]. This neurogenesis was shown to be de-regulated by infection with neurovirulent viruses causing Borna disease and Varicella-zoster [20,21]. Thus, it would be essential to determine whether infection by H5N1 virus occurs in neural progenitor cells, and if so, whether such infection plays a role in the pathogenesis of H5N1-induced encephalopathy. In order to shed light on these questions relevant to the pathogeneses of influenza virus-induced neuropathology, we infected human neural progenitor cells (hNPCs) with H5N1 avian influenza virus and examined the resulting virus-cell interactions, the induction of cellular mediators, and the phenotypic characterizations of hNPCs following H5N1 virus infection in vitro.