Single mutation in the matrix gene of seasonal influenza A viruses critically affects the performance of diagnostic molecular assay.

Reduced intensity of the fluorescence signal in the amplification curve was observed when using a WHO recommended real time RT-PCR for influenza virus detection. A single mutation, G189T, in the conserved region of influenza virus matrix gene was detected by Sanger sequencing. The mutation is located in the probe binding region, hence we speculated it could be the reason for the atypical shape of amplification curve.