Pathology of highly pathogenic avian influenza virus H5N1 infection in red knots.

Lesions of acute pancreatitis, showing a discrete focus of pancreatic exocrine cell necrosis (A); lesions of acute encephalitis, showing perivascular accumulation of lymphocytes (B); and presence of influenza virus antigen in nuclei of neurons (large cells) and glial cells (small cells; C). Slides were stained with hematoxylin and eosin (A and B), or by immunohistochemistry using a monoclonal antibody against the nucleoprotein of influenza A virus as the primary antibody (C).