Definitive diagnosis relies on viral isolation and characterization. For virus characterization, the methodology using genomic amplification (PCR), firstly by the reverse transcription of viral RNA into cDNA, the cyclic amplification of cDNA and sequencing of products, will enable very precise description of strains, according to the oligonucleotide primers designed and target gene. Broadly sensitive universal gene targets are the nucleoprotein, the matrix or the S2 encoding genes. The S1 encoding gene products sequencing may enable phylogenetic results which are comparable to serotyping. Methods for IBV antigens detection may employ labelled antibodies, such as direct immunofluorescence or immunoperoxidase. Antibodies to IBV may be detected by indirect immunofluorescent antibody test, ELISA and Haemagglutination inhibition (haemagglutinating IBV produced after enzymatic treatment by phospholipase C).