Cover photograph (Copyright © 2004, American Society for Microbiology. All Rights Reserved.): Immunostaining of cells infected by human influenza virus (red) in fully differentiated cultures of human airway epithelium. Black staining displays cilia of ciliated cells. Cells were counterstained with Alcian Blue, periodic acid-Schiff reagent, and hematoxylin. (See related article on page 12665.)