Beside a secondary, clinically latent salivary virus secretion, differentiation can be made between concomitant sialadenitis induced by various viruses and viral sialadenitis showing characteristic and/or pathognomonic morphological and clinical features, whereby sialadenotropism must also be present. Viremia induces a viral inflammatory reaction via a local cytopathogenetic effect. Clinically important viral diseases include epidemic parotitis (mumps), cytomegaly and HIV infection presenting with large lymphoepithelial cystic lesions.