Gubareva LV, et al. – Here authors sought to provide the global update on the susceptibility of human influenza viruses to neuraminidase inhibitors, 2015–2016. Overall, it was observed that the vast majority (>99%) of the viruses tested by WHO Collaborating Centres (WHO CCs) were susceptible to all four neuraminidase inhibitors (NAIs), showing normal inhibition (NI). Hence, NAIs were recommended for the treatment of influenza virus infections. Nevertheless, the data suggested continued drug susceptibility monitoring using both NAI assay and sequence analysis as indispensable.

• Four World Health Organization (WHO) Collaborating Centres for Reference and Research on Influenza and one WHO Collaborating Centre for the Surveillance, Epidemiology and Control of Influenza (WHO CCs) assessed antiviral susceptibility of 14,330 influenza A and B viruses collected by WHO–recognized National Influenza Centres (NICs) between May 2015 and May 2016.
• Researchers used Neuraminidase (NA) inhibition assay to determine 50% inhibitory concentration (IC50) data for NA inhibitors (NAIs) oseltamivir, zanamivir, peramivir and laninamivir.
• In addition, they retrieved NA sequences from 13,484 influenza viruses from public sequence databases and screened them for amino acid substitutions (AAS) associated with reduced inhibition (RI) or highly reduced inhibition (HRI) by NAIs.
• 93% of the viruses tested by WHO CCs were from three WHO regions: Western Pacific, the Americas and Europe.
• RI or HRI was exhibited in approximately 0.8% (n = 113) by at least one of four NAIs.
• In common with the previous seasons, the most common NA AAS was H275Y in A(H1N1)pdm09 viruses, which indicated HRI by oseltamivir and peramivir.
• Two A(H1N1)pdm09 viruses were observed to carry a rare NA AAS, S247R, it seemed to confer RI/HRI by the four NAIs.
• Findings revealed that the overall frequency of A(H1N1)pdm09 viruses containing NA AAS associated with RI/HRI was approximately 1.8% (125/6915), which was slightly higher than in the previous 2014–15 season (0.5%).
• A new AAS, NA H134N was identified in three B/Victoria–lineage viruses, that conferred HRI by zanamivir and laninamivir, and borderline HRI by peramivir.
• A single B/Victoria–lineage virus seemed to harbour NA G104E, which was associated with HRI by all four NAIs.
• Among type B viruses, the overall frequency of RI/HRI phenotype was approximately 0.6% (43/7677), which is lower than that in the previous season.