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. 2020 Nov;14(6):700-709.
doi: 10.1111/irv.12772. Epub 2020 Jun 17.

Comparative epidemiology, phylogenetics, and transmission patterns of severe influenza A/H3N2 in Australia from 2003 to 2017

Jing Xia  1   2 , Dillon C Adam  1 , Aye Moa  1 , Abrar A Chughtai  3 , Ian G Barr  4   5 , Naomi Komadina  4   6 , C Raina MacIntyre  1
Affiliations

Comparative epidemiology, phylogenetics, and transmission patterns of severe influenza A/H3N2 in Australia from 2003 to 2017

Jing Xia et al. Influenza Other Respir Viruses. 2020 Nov.

Abstract

Background: Over the last two decades, Australia has experienced four severe influenza seasons caused by a predominance of influenza A (A/H3N2): 2003, 2007, 2012, and 2017.

Methods: We compared the epidemiology, genetics, and transmission dynamics of severe A/H3N2 seasons in Australia from 2003 to 2017.

Results: Since 2003, the proportion of notifications in 0-4 years old has decreased, while it has increased in the age group >80 years old (P < .001). The genetic diversity of circulating influenza A/H3N2 viruses has also increased over time with the number of single nucleotide polymorphisms significantly (P < .05) increasing. We also identified five residue positions within or near the receptor binding site of HA (144, 145, 159, 189, and 225) undergoing frequent mutations that are likely involved in significant antigenic drift and possibly severity. The Australian state of Victoria was identified as a frequent location for transmission either to or from other states and territories over the study years. The states of New South Wales and Queensland were also frequently implicated as locations of transmission to other states and territories but less so over the years. This indicates a stable but also changing dynamic of A/H3N2 circulation in Australia.

Conclusion: These results have important implications for future influenza surveillance and control policy in the country. Reasons for the change in age-specific infection and increased genetic diversity of A/H3N2 viruses in recent years should be explored.

Keywords: Australia; H3N2 subtype; epidemiology; influenza A virus; phylogeography; public health.

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Figures

FIGURE 1
FIGURE 1
Notification rate of laboratory‐confirmed influenza (per 100 000 population), Australia, by 5‐year age group. A: 2003. B: 2007. C: 2012. D: 2017. Black bars represent the total number of influenza notifications by age group while red bars represent type A notifications, and grey bars represent type B notifications. The separate notification rate of type A and type B were not available in 2003 and 2007 seasons. Data source: NNDSS
FIGURE 2
FIGURE 2
A, Timeline of mutations by season. Blue bars represent the proportion among taxa per season and red superscript represents the relative HA epitope. Blue boxes highlight sites that mutated at least twice and # represents the sites located on RBS and edge of RBS of HA protein. B, Mutations relative to vaccine‐strains (red dotted arrow) and HA sites under strong positive selection by season (blue dotted arrow). Percentage represents the proportion of taxa within that subclade each season
FIGURE 3
FIGURE 3
HA maximum clade credibility (MCC) phylogeographic tree of 2003, 2007, 2012, and 2017 A/H3N2 seasons. Branches were colored according to the most probable locations at which the nodes were formed. A, 2003 season, B, 2007 season, C, 2012 season, D, 2017 season
FIGURE 4
FIGURE 4
Phylogeographic projection of supported routes of influenza A/H3N2 transmission between states and territories in based on HA across four predominant H3 seasons
See this image and copyright information in PMC

References

    1. Nelson MI, Holmes EC. The evolution of epidemic influenza. Nat Rev Genet. 2007;8(3):196‐205. - PubMed
    1. Moa A, Muscatello D, Chughtai A, Chen X, MacIntyre CR. Flucast: a real‐time tool to predict severity of an influenza season. JMIR Public Health Surveill. 2019;5(3):e11780. - PMC - PubMed
    1. Kelly HA, Sullivan SG, Grant KA, Fielding JE. Moderate influenza vaccine effectiveness with variable effectiveness by match between circulating and vaccine strains in Australian adults aged 20–64 years, 2007–2011. Influenza Other Respir Viruses. 2013;7(5):729‐737. - PMC - PubMed
    1. Thompson WW, Shay DK, Weintraub E, et al. Influenza‐associated hospitalizations in the United States. JAMA. 2004;292(11):1333‐1340. - PubMed
    1. Matias G, Taylor R, Haguinet F, Schuck‐Paim C, Lustig R, Shinde V. Estimates of hospitalization attributable to influenza and RSV in the US during 1997–2009, by age and risk status. BMC Public Health. 2017;17(1):271. - PMC - PubMed

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