A novel means of identifying the neuraminidase type of currently circulating human A(H1) influenza viruses

With the recent emergence and spread of influenza A(H1N2) viruses which appear to have arisen by reassortment of circulating A(H1N1) and A(H3N2) strains, there is a need in epidemiological studies to determine the neuraminidase type in order to differentiate between influenza A(H1N2) and A(H1N1) strains. A fluorescence-based neuraminidase enzyme inhibition assay that has been developed to screen influenza viruses for potential resistance to the neuraminidase inhibitor drugs appears to be suitable for this purpose. When used with the neuraminidase inhibitor zanamivir the assay was able to provide a positive predictive value of 93.5% for the identification of neuraminidase type N1 or N2. This assay enables a large number of influenza A viruses to be screened at low cost to determine relative levels of A(H1N2) or A(H1N1) viruses circulating in the population.