<prompt> Electron microscopy is helpful in diagnosis of -RotavirusRSVHerpesvirusPrion  <response>: Laboratory diagnosis of rotavirus include electron microscooy and immunielectron microscopy-these are expensive and comolicated procedures.concentration of more than 106 paicles per ml are necessary for the virus to be seen in feces by elwctron microscopy. REF:ANANTHANARAYAN AND PANIKERS TEXTBOOK OF MICROBIOLOGY 9TH EDITION PAGE NO:561 