Report on influenza viruses received and tested by the Melbourne WHO Collaborating Centre for Reference and Research on Influenza in 2019.

ABSTRACT: As part of its role in the World Health Organization's (WHO) Global Influenza Surveillance and Response System (GISRS), the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne received a record total of 9,266 human influenza positive samples during 2019. Viruses were analysed for their antigenic, genetic and antiviral susceptibility properties. Selected viruses were propagated in qualified cells or embryonated hen's eggs for potential use in seasonal influenza virus vaccines. In 2019, influenza A(H3N2) viruses predominated over influenza A(H1N1)pdm09 and B viruses, accounting for a total of 51% of all viruses analysed. The majority of A(H1N1)pdm09, A(H3N2) and influenza B viruses analysed at the Centre were found to be antigenically similar to the respective WHO recommended vaccine strains for the Southern Hemisphere in 2019. However, phylogenetic analysis indicated that a significant proportion of circulating A(H3N2) viruses had undergone genetic drift relative to the WHO recommended vaccine strain for 2019. Of 5,301 samples tested for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir, four A(H1N1)pdm09 viruses showed highly reduced inhibition with oseltamivir, one A(H1N1)pdm09 virus showed highly reduced inhibition with zanamivir and three B/Victoria viruses showed highly reduced inhibition with zanamivir.

The molecular epidemiology of norovirus outbreaks in Victoria, 2016.

Noroviruses are a leading cause of outbreaks of gastroenteritis. This study examined the incidence and molecular characteristics of norovirus outbreaks in Victoria, Australia in 2016. Norovirus was detected in 52.4% of gastroenteritis outbreaks surveyed and the year was notable in that there was no significant temporal peak in norovirus outbreaks. Norovirus Open Reading Frame (ORF)2 (capsid) genotypes were successfully identified in 84 of 110 norovirus outbreaks and included GI.3, GI.6, GI.9, GII.2, GII.3, GII.4, GII.6, and GII.17. Norovirus GII.4 was the most common ORF2 genotype detected (55.9%). Other relatively common ORF2 genotypes included GII.2 (19.0%), GII.17 (9.5%), GI.3 (7.1%) and GII.3 (4.8%). The GII.P4_NewOrleans_2009/GII.4_Sydney_2012 recombinant emerged as an important new GII.4 form. The study also confirmed the identity of three ORF1/ORF2 recombinant forms as follows: GII.P16/GII.2, GII.P16/GII.3 and GII.P16/GII.4. Statistical analysis indicated GII.4 (ORF2) was much more common in healthcare settings than in non-healthcare settings. The study indicates 2016 was a transition year in Victoria, Australia, in that the previous norovirus epidemic strain had diminished to the point where it was no longer dominant but as yet no replacement epidemic strain had become obvious.