Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 38 4 2009 12 15 29 34 E Saberfar A Najafi Z Goodarzi H Lashini 2015 10 03 Background: Avian influenza virus (AIV) infection is a major cause of bird and human morbidity and mortality. We aimed to evaluate a specific and sensitive multiplex RT-PCR that can simultaneously detect influenza type A viruses and differenti­ate the two most important subtypes of avian influenza viruses H7 and H9 subtypes. Methods: A multiplex reverse transcriptase-polymerase chain reaction (mRT-PCR) was developed and optimized for the detec­tion of type A influenza virus. Simultaneously avian H7 and H9 hemagglutinin subtypes was differentiated. Three sets of specific oligonucleotide primers were used in this test for type A influenza virus, H7 and H9 heamagglutinin subtypes. Results: The mRT-PCR DNA products were visualized by gel electrophoresis and consisted of fragments of 313 bp for H7 and 428 bp for H9 hemagglutinin subtypes, and 101 bp for type A influenza virus. The common set of primers for type A influ­enza virus were able to amplify a 101 bp DNA band for any of the other subtypes of influenza A virus. Conclusion: The mRT-PCR assay developed in this study was found to be sensitive and specific.  No specific amplification bands of the same sizes (313 and 428 bp) could be amplified for RNA of other influenza hemagglutinin subtypes, nor spe­cific amplification bands of type A influenza (101 bp) for Influenza B, C, or other viral or bacterial pathogens tested in this study. https://ijph.tums.ac.ir/index.php/ijph/article/view/3147 https://ijph.tums.ac.ir/index.php/ijph/article/download/3147/2946