Evolution and rapid spread of a reassortant A(H3N2) virus that predominated the 2017–2018 influenza season

Abstract The 2017–2018 North American influenza season caused more hospitalizations and deaths than any year since the 2009 H1N1 pandemic. The majority of recorded influenza infections were caused by A(H3N2) viruses, with most of the virus’s North American diversity falling into the A2 clade. Within A2, we observe a subclade which we call A2/re that rose to comprise almost 70 per cent of A(H3N2) viruses circulating in North America by early 2018. Unlike most fast-growing clades, however, A2/re contains no amino acid substitutions in the hemagglutinin (HA) segment. Moreover, hemagglutination inhibition assays did not suggest substantial antigenic differences between A2/re viruses and viruses sampled during the 2016–2017 season. Rather, we observe that the A2/re clade was the result of a reassortment event that occurred in late 2016 or early 2017 and involved the combination of the HA and PB1 segments of an A2 virus with neuraminidase (NA) and other segments a virus from the clade A1b. The success of this clade shows the need for antigenic analysis that targets NA in addition to HA. Our results illustrate the potential for non-HA drivers of viral success and necessitate the need for more thorough tracking of full viral genomes to better understand the dynamics of influenza epidemics.

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Evolution and rapid spread of a reassortant A(H3N2) virus that predominated the 2017-2018 influenza season

10.1101/543322 ◽

2019 ◽

Author(s):

Barney I. Potter ◽

Rebecca Garten ◽

James Hadfield ◽

John Huddleston ◽

John Barnes ◽

...

Keyword(s):

North American ◽

Influenza Season ◽

H3n2 Virus ◽

Amino Acid Substitutions ◽

H1n1 Pandemic ◽

Reassortment Event ◽

Antigenic Analysis ◽

Viral Genomes ◽

Rapid Spread ◽

2009 H1n1

The 2017-2018 North American influenza season caused more hospitalizations and deaths than any year since the 2009 H1N1 pandemic. The majority of recorded influenza infections were caused by A(H3N2) viruses, with most of the virus’s North American diversity falling into the A2 clade. Within A2, we observe a subclade which we call A2/re that rose to comprise almost 70% of A(H3N2) viruses circulating in North America by early 2018. Unlike most fast-growing clades, however, A2/re contains no amino acid substitutions in the hemagglutinin (HA) segment. Moreover, HI assays did not suggest substantial antigenic differences between A2/re viruses and viruses sampled during the 2016-2017 season. Rather, we observe that the A2/re clade was the result of a reassortment event that occurred in late 2016 or early 2017 and involved the combination of the HA and PB1 segments of an A2 virus with neuraminidase (NA) and other segments a virus from the clade A1b. The success of this clade shows the need for antigenic analysis that targets NA in addition to HA. Our results illustrate the potential for non-HA drivers of viral success and necessitate the need for more thorough tracking of full viral genomes to better understand the dynamics of influenza epidemics.

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Genetic and antigenic characterisation of influenza A(H3N2) viruses isolated in Yokohama during the 2016/17 and 2017/18 influenza seasons

Eurosurveillance ◽

10.2807/1560-7917.es.2019.24.6.1800467 ◽

2019 ◽

Vol 24 (6) ◽

Cited By ~ 4

Author(s):

Chiharu Kawakami ◽

Seiya Yamayoshi ◽

Miki Akimoto ◽

Kazuya Nakamura ◽

Hideka Miura ◽

...

Keyword(s):

Immune Responses ◽

Influenza A ◽

Influenza Season ◽

Glycosylation Site ◽

H3n2 Virus ◽

Amino Acid Substitutions ◽

Antigenic Analysis ◽

Glycosylation Sites ◽

Identify Amino Acid ◽

Human Immune

Background: Influenza A(H3N2) virus rapidly evolves to evade human immune responses, resulting in changes in the antigenicity of haemagglutinin (HA). Therefore, continuous genetic and antigenic analyses of A(H3N2) virus are necessary to detect antigenic mutants as quickly as possible. Aim: We attempted to phylogenetically and antigenically capture the epidemic trend of A(H3N2) virus infection in Yokohama, Japan during the 2016/17 and 2017/18 influenza seasons. Methods: We determined the HA sequences of A(H3N2) viruses detected in Yokohama, Japan during the 2016/17 and 2017/18 influenza seasons to identify amino acid substitutions and the loss or gain of potential N-glycosylation sites in HA, both of which potentially affect the antigenicity of HA. We also examined the antigenicity of isolates using ferret antisera obtained from experimentally infected ferrets. Results: Influenza A(H3N2) viruses belonging to six clades (clades 3C.2A1, 3C.2A1a, 3C.2A1b, 3C.2A2, 3C.2A3 and 3C.2A4) were detected during the 2016/17 influenza season, whereas viruses belonging to two clades (clades 3C.2A1b and 3C.2A2) dominated during the 2017/18 influenza season. The isolates in clades 3C.2A1a and 3C.2A3 lost one N-linked glycosylation site in HA relative to other clades. Antigenic analysis revealed antigenic differences among clades, especially clade 3C.2A2 and 3C.2A4 viruses, which showed distinct antigenic differences from each other and from other clades in the antigenic map. Conclusion: Multiple clades, some of which differed antigenically from others, co-circulated in Yokohama, Japan during the 2016/17 and 2017/18 influenza seasons.

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SARIMA-modelled greater severity and mortality during the 2010/11 post-pandemic influenza season compared to the 2009 H1N1 pandemic in English hospitals

International Journal of Infectious Diseases ◽

10.1016/j.ijid.2021.01.070 ◽

2021 ◽

Vol 105 ◽

pp. 161-171

Author(s):

Krystal Lau ◽

Ilaria Dorigatti ◽

Marisa Miraldo ◽

Katharina Hauck

Keyword(s):

Pandemic Influenza ◽

Influenza Season ◽

H1n1 Pandemic ◽

2009 H1n1

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Influenza vaccination coverage among US-Mexico land border crossers: 2009 H1N1 pandemic and 2011–2012 influenza season

Travel Medicine and Infectious Disease ◽

10.1016/j.tmaid.2018.10.002 ◽

2019 ◽

Vol 27 ◽

pp. 99-103

Author(s):

Alfonso Rodriguez-Lainz ◽

Carla DeSisto ◽

Stephen Waterman ◽

Monica Sovero Wiedemann ◽

Conschetta Wright Moore ◽

...

Keyword(s):

Influenza Vaccination ◽

Vaccination Coverage ◽

Influenza Season ◽

H1n1 Pandemic ◽

2009 H1n1 ◽

Border Crossers

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Tobacco smoking and influenza (review)

MedAlliance ◽

10.36422/23076348-2020-8-1-90-92 ◽

2020 ◽

Vol 8 (1) ◽

pp. 90-92

Keyword(s):

Risk Factors ◽

Influenza Infection ◽

H1n1 Pandemic ◽

Influenza Epidemic ◽

Risk Of Death ◽

Stop Smoking ◽

2009 H1n1 ◽

Former Smokers ◽

The Russian Federation ◽

Pandemic Flu

The review analyzed data on the risks of influenza infection and severe course in tobacco smokers compared with non-smokers. The incidence of influenza in the Russian Federation in 2018 amounted to 26.33 per 100 000 people, and was 24% lower than the incidence in 2017 (34.86 per 100 000) due to the fact that in recent years the coverage of the population with preventive vaccinations has been significantly increased against the flu. Meta-analyzes shows that current smokers are more likely to get the flu than non-smokers. It is noted that smoking may increase the risk of hospitalization in smokers (OR 1.32–2.18 in various meta-analyzes) and former smokers after infection with the influenza virus. Tobacco has been found to increase the risk of death from influenza among older people. At the same time, there is a study of risk factors for severe outcomes in patients hospitalized with the 2009 H1N1 pandemic flu, in which smoking was not a risk factor for severe outcomes. During the influenza epidemic, smokers and former smokers should be given the flu shot and be informed of the risk of hospitalization, and they are also strongly advised to stop smoking.

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