Laboratory diagnosis of viral infections purpose test for viral infection in the diagnostic laboratory virus infections can be confirmed by a multitude of methods diagnostic virology has changed rapidly due to the advent of molecular techniques and increased clinical sensitivity of serological assays. The serologic tests most often used in veterinary diagnostic laboratories to diagnose viral infections are serum neutralization sn tests hemagglutination inhibition hi tests agar gel immunodiffusion agid tests and enzyme linked. Rationale for specific diagnosis why bother to establish a definitive laboratory diagnosis of . The diagnosis of a viral infection can be established in several ways often used together namely detection of virus particles in specimen taken from the appropriate site detection of viral antigens ag in blood or body fluids serological procedure to detect specific anti viral antibodies rise