#Epidemiology and #Genotypic #Diversity of #EA #Avian-Like #H1N1 #Swine #Influenza Viruses in #China (Virol Sin., abstract)

[Source: Virologica Sinica, full page: (LINK). Abstract, edited.]

Epidemiology and Genotypic Diversity of Eurasian Avian-Like H1N1 Swine Influenza Viruses in China

Zhaomin Feng, Wenfei Zhu, Lei Yang, Jia Liu, Lijuan Zhou, Dayan Wang & Yuelong Shu

Virologica Sinica (2020)



Eurasian avian-like H1N1 (EA H1N1) swine influenza virus (SIV) outside European countries was first detected in Hong Kong Special Administrative Region (Hong Kong, SAR) of China in 2001. Afterwards, EA H1N1 SIVs have become predominant in pig population in this country. However, the epidemiology and genotypic diversity of EA H1N1 SIVs in China are still unknown. Here, we collected the EA H1N1 SIVs sequences from China between 2001 and 2018 and analyzed the epidemic and phylogenic features, and key molecular markers of these EA H1N1 SIVs. Our results showed that EA H1N1 SIVs distributed in nineteen provinces/municipalities of China. After a long-time evolution and transmission, EA H1N1 SIVs were continuously reassorted with other co-circulated influenza viruses, including 2009 pandemic H1N1 (A(H1N1)pdm09), and triple reassortment H1N2 (TR H1N2) influenza viruses, generated 11 genotypes. Genotype 3 and 5, both of which were the reassortments among EA H1N1, A(H1N1)pdm09 and TR H1N2 viruses with different origins of M genes, have become predominant in pig population. Furthermore, key molecular signatures were identified in EA H1N1 SIVs. Our study has drawn a genotypic diversity image of EA H1N1 viruses, and could help to evaluate the potential risk of EA H1N1 for pandemic preparedness and response.

Keywords: Avian Influenza; Swine Influenza; Influenza A; Reassortant strain; Pigs; H1N1; H1N2; H1N1pdm09; China.


Prevalent #Eurasian #avian-like #H1N1 #swine #influenza virus with #H1N1pdm09 viral #genes facilitating #human infection (Proc Natl Acad Sci USA, abstract)

[Source: Proceedings of the National Academy of Sciences of the United States of America, full page: (LINK). Abstract, edited.]

Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection

Honglei Sun, Yihong Xiao,  Jiyu Liu, Dayan Wang, Fangtao Li, Chenxi Wang, Chong Li, Junda Zhu, Jingwei Song, Haoran Sun,  Zhimin Jiang, Litao Liu, Xin Zhang, Kai Wei, Dongjun Hou, Juan Pu, Yipeng Sun, Qi Tong, Yuhai Bi, Kin-Chow Chang, Sidang Liu,  George F. Gao, and Jinhua Liu

PNAS first published June 29, 2020 https://doi.org/10.1073/pnas.1921186117

Contributed by George F. Gao, April 28, 2020 (sent for review December 9, 2019; reviewed by Ian H. Brown and Xiu-Feng Henry Wan)



Pigs are intermediate hosts for the generation of pandemic influenza virus. Thus, systematic surveillance of influenza viruses in pigs is a key measure for prewarning the emergence of the next pandemic influenza. Here, we identified a reassortant EA H1N1 virus possessing pdm/09 and TR-derived internal genes, termed as G4 genotype, which has become predominant in swine populations since 2016. Similar to pdm/09 virus, G4 viruses have all the essential hallmarks of a candidate pandemic virus. Of concern is that swine workers show elevated seroprevalence for G4 virus. Controlling the prevailing G4 EA H1N1 viruses in pigs and close monitoring in human populations, especially the workers in swine industry, should be urgently implemented.



Pigs are considered as important hosts or “mixing vessels” for the generation of pandemic influenza viruses. Systematic surveillance of influenza viruses in pigs is essential for early warning and preparedness for the next potential pandemic. Here, we report on an influenza virus surveillance of pigs from 2011 to 2018 in China, and identify a recently emerged genotype 4 (G4) reassortant Eurasian avian-like (EA) H1N1 virus, which bears 2009 pandemic (pdm/09) and triple-reassortant (TR)-derived internal genes and has been predominant in swine populations since 2016. Similar to pdm/09 virus, G4 viruses bind to human-type receptors, produce much higher progeny virus in human airway epithelial cells, and show efficient infectivity and aerosol transmission in ferrets. Moreover, low antigenic cross-reactivity of human influenza vaccine strains with G4 reassortant EA H1N1 virus indicates that preexisting population immunity does not provide protection against G4 viruses. Further serological surveillance among occupational exposure population showed that 10.4% (35/338) of swine workers were positive for G4 EA H1N1 virus, especially for participants 18 y to 35 y old, who had 20.5% (9/44) seropositive rates, indicating that the predominant G4 EA H1N1 virus has acquired increased human infectivity. Such infectivity greatly enhances the opportunity for virus adaptation in humans and raises concerns for the possible generation of pandemic viruses.

swine influenza – Eurasian avian-like H1N1 virus – 2009 pandemic H1N1 virus – reassortant – pandemic potential



1 H.S., Y.X., and J.L. contributed equally to this work.

2 To whom correspondence may be addressed. Email: gaof@im.ac.cn or ljh@cau.edu.cn.

Author contributions: Honglei Sun, Y.X., S.L., G.F.G., and Jinhua Liu designed research; Honglei Sun, Y.X., Jiyu Liu, F.L., C.L., J.Z., J.S., Haoran Sun, Z.J., L.L., X.Z., K.W., D.H., and Q.T. performed research; Honglei Sun, Jiyu Liu, D.W., C.W., J.P., Y.B., and Jinhua Liu analyzed data; and Honglei Sun, J.P., Y.S., K.-C.C., G.F.G., and Jinhua Liu wrote the paper.

Reviewers: I.H.B., Animal and Plant Health Agency; and X.-F.H.W., University of Missouri.

The authors declare no competing interest.

Data deposition: The sequences generated in this study have been deposited in the GenBank database (accession nos. are listed in SI Appendix, Table S3).

This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.1921186117/-/DCSupplemental.

Published under the PNAS license.

Keywords: Influenza A; Reassortant strain; Avian Influenza; Swine Influenza; Pigs; Human; China; H1N1; H1N1pdm09.


#Molecular Characterization and Three-Dimensional #Structures of #Avian #H8, #H11, #H14, #H15 and #Swine #H4 #Influenza Virus #Hemagglutinins (Heliyon, abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Heliyon. 2020 Jun 6;6(6):e04068. doi: 10.1016/j.heliyon.2020.e04068. eCollection 2020 Jun.

Molecular Characterization and Three-Dimensional Structures of Avian H8, H11, H14, H15 and Swine H4 Influenza Virus Hemagglutinins

Hua Yang 1, Paul J Carney 1, Jessie C Chang 1, James Stevens 1

Affiliation: 1 Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA.

PMID: 32529072 PMCID: PMC7281811 DOI: 10.1016/j.heliyon.2020.e04068



Of the eighteen hemagglutinin (HA) subtypes (H1-H18) that have been identified in bats and aquatic birds, many HA subtypes have been structurally characterized. However, several subtypes (H8, H11 and H12) still require characterization. To better understand all of these HA subtypes at the molecular level, HA structures from an A(H4N6) (A/swine/Missouri/A01727926/2015), an A(H8N4) (A/turkey/Ontario/6118/1968), an A(H11N9) (A/duck/Memphis/546/1974), an A(H14N5) A/mallard/Gurjev/263/1982, and an A(H15N9) (A/wedge-tailed shearwater/Western Australia/2576/1979 were determined by X-ray crystallography at 2.2Å, 2.3Å, 2.8Å, 3.0Å and 2.5Å resolution, respectively. The interactions between these viruses and host receptors were studied utilizing glycan-binding analyses with their recombinant HA. The data show that all avian HAs retain their strict binding preference to avian receptors, whereas swine H4 has a weak human receptor binding. The molecular characterization and structural analyses of the HA from these zoonotic influenza viruses not only provide a deeper appreciation and understanding of the structure of all HA subtypes, but also re-iterate why continuous global surveillance is needed.

Keywords: A(H11N9); A(H14N5); A(H15N9); A(H4N6); A(H8N4); Avian; Biomolecules; Glycobiology; Hemagglutinin; Influenza virus; Microbiology; Proteins; Receptor binding; Swine; Viral protein; Virology.

Keywords: Influenza A; Avian Influenza; Swine Influenza; H8N4; H4N6; H11N9; H14N5; H15N9.


#Aerosol #transmission from infected #swine to #ferrets of an #H3N2 virus collected from an #agricultural #fair and associated with #human variant infections (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

Aerosol transmission from infected swine to ferrets of an H3N2 virus collected from an agricultural fair and associated with human variant infections

Bryan S. Kaplan, J. Brian Kimble, Jennifer Chang, Tavis K. Anderson, Phillip C. Gauger, Alicia Janas-Martindale, Mary Lea Killian, Andrew S. Bowman, Amy L. Vincent

DOI: 10.1128/JVI.01009-20



Influenza A viruses (IAV) sporadically transmit from swine to humans, typically associated with agricultural fairs in the USA. A human seasonal H3 from the 2010-2011 IAV season was introduced into the US swine population and termed H3.2010.1 to differentiate from the previous swine H3. This H3N2 lineage became widespread in the US commercial swine population, subsequently spilling over into exhibition swine, and caused a majority of H3N2 variant (H3N2v) cases in humans in 2016 and 2017. A cluster of human H3N2v cases were reported at an agricultural fair in Ohio in 2017 where 2010.1 H3N2 IAV was concurrently detected in exhibition swine. Genomic analysis showed the swine and human isolates were nearly identical. Here we evaluated the propensity of a 2010.1 H3N2 IAV (A/swine/Ohio/A01354299/2017; sw/OH/2017) isolated from a pig in the agricultural fair outbreak to replicate in ferrets and transmit from swine to ferret. Sw/OH/2017 displayed robust replication in the ferret respiratory tract, causing slight fever and moderate weight loss. Further, sw/OH/2017 was capable of efficient respiratory droplet transmission from infected pigs to contact ferrets. These findings establish a model for evaluating the propensity of swine IAV to transmit from pig-to-ferret as a measure of risk to the human population. The identification of higher risk swine strains can then be targeted for control measures to limit the dissemination at human-swine interfaces to reduce the risk of zoonotic infections and inform pandemic planning.



A recently emerged lineage of human-like H3N2 (H3.2010.1) influenza A virus (IAV) from swine have been frequently detected in commercial and exhibition swine in recent years and were associated with H3N2 variant cases in humans from 2016 and 2017. To demonstrate a model for characterizing the potential for zoonotic transmission associated with swine IAV, we performed an in vivo transmission study between pigs infected with an H3.2010.1 H3N2 and aerosol contact ferrets. The efficient interspecies transmission demonstrated for the H3.2010.1 IAV-S emphasizes the need for further characterization of viruses circulating at the swine-human interface for transmission potential prior to human spillover and the development and implementation of more robust vaccines and control strategies to mitigate human exposure to higher risk swine strains.

This is a work of the U.S. Government and is not subject to copyright protection in the United States. Foreign copyrights may apply.

Keywords: Swine Influenza; Influenza A; H3N2; Reassortant strain; Pigs; Human; USA; Animal models.


#Genetic characterization of #influenza A viruses in #Japanese #swine during 2015–2019 (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

Genetic characterization of influenza A viruses in Japanese swine during 2015–2019

Junki Mine, Yuko Uchida, Nobuhiro Takemae, Takehiko Saito

DOI: 10.1128/JVI.02169-19



To assess the current status of influenza A viruses of swine (IAVs-S) throughout Japan and to investigate how these viruses persisted and evolve on pig farms, we genetically characterized IAVs-S isolated during 2015–2019. Nasal swab samples collected through active surveillance and lung tissue samples collected for diagnosis yielded 424 IAVs-S—comprising 78 H1N1, 331 H1N2, and 15 H3N2 viruses—from farms in sampled 21 prefectures in Japan. Phylogenetic analyses of surface genes revealed that the 1A.1 classical swine H1 lineage has evolved uniquely since the late 1970s among pig populations in Japan. During 2015–2019, A(H1N1)pdm09 viruses repeatedly become introduced into farms and reassorted with endemic H1N2 and H3N2 IAVs-S. H3N2 IAVs-S isolated during 2015–2019 formed a clade that originated from 1999–2000 human seasonal influenza viruses; this situation differs from previous reports, in which H3N2 IAVs-S derived from human seasonal influenza viruses were transmitted sporadically from humans to swine but then disappeared without becoming established within the pig population. At farms where IAVs-S were frequently isolated for at least 3 years, multiple introductions of IAVs-S with phylogenetically distinct HA genes occurred. In addition, at one farm, IAVs-S derived from a single introduction persisted for at least 3 years and carried no mutations at the deduced antigenic sites of the hemagglutinin protein except only one at the antigenic site (Sa). Our results extend our understanding regarding the status of IAVs-S currently circulating in Japan and how they genetically evolve at the farm level.



Understanding the current status of influenza A viruses of swine (IAVs-S) and their evolution at the farm level is important for controlling these pathogens. Efforts to monitor IAVs-S during 2015–2019 yielded H1N1, H1N2, and H3N2 viruses. H1 genes in Japanese swine formed unique clade in the classical swine H1 lineage of 1A.1, and H3 genes originating from 1999–2000 human seasonal influenza viruses appear to have become established among Japanese swine. A(H1N1)pdm09-derived H1 genes became introduced repeatedly and reassorted with endemic IAVs-S, resulting in various combinations of surface and internal genes among pig populations in Japan. At the farm level, multiple introductions of IAVs-S with phylogenetically distinct HA sequences occurred, or IAVs-S derived from a single introduction have persisted for at least 3 years with only a single mutation at the antigenic site of the HA protein. Continued monitoring of IAVs-S is necessary to update and maximize control strategies.

Copyright © 2020 Mine et al.

This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.

Keywords: Influenza A; H1N1pdm09; H1N2; H3N2; Swine Influenza; Reassortant strain; Pigs; Japan.


Higher #virulence of #swine #H1N2 #influenza viruses containing #avian-origin #HA and 2009 #pandemic PA and NP in #pigs and mice (Arch Virol., abstract)

[Source: Archives of Virology, full page: (LINK). Abstract, edited.]

Higher virulence of swine H1N2 influenza viruses containing avian-origin HA and 2009 pandemic PA and NP in pigs and mice

Yunyueng Jang, Taehyun Seo & Sang Heui Seo

Archives of Virology (2020)



Pigs are capable of harbouring influenza A viruses of human and avian origin in their respiratory tracts and thus act as an important intermediary host to generate novel influenza viruses with pandemic potential by genetic reassortment between the two viruses. Here, we show that two distinct H1N2 swine influenza viruses contain avian-like or classical swine-like hemagglutinins with polymerase acidic (PA) and nucleoprotein (NP) genes from 2009 pandemic H1N1 influenza viruses that were found to be circulating in Korean pigs in 2018. Swine H1N2 influenza virus containing an avian-like hemagglutinin gene had enhanced pathogenicity, causing severe interstitial pneumonia in infected pigs and mice. The mortality rate of mice infected with swine H1N2 influenza virus containing an avian-like hemagglutinin gene was higher by 100% when compared to that of mice infected with swine H1N2 influenza virus harbouring classical swine-like hemagglutinin. Further, chemokines attracting inflammatory cells were strongly induced in lung tissues of pigs and mice infected by swine H1N2 influenza virus containing an avian-like hemagglutinin gene. In conclusion, it is necessary for the well-being of humans and pigs to closely monitor swine influenza viruses containing avian-like hemagglutinin with PA and NP genes from 2009 pandemic H1N1 influenza viruses.

Keywords: Influenza A; Avian Influenza; Swine Influenza; H1N1pdm09; H1N2; Reassortant strain; Pigs; Animal models.


#Human #infection with a novel #reassortant #Eurasian-avian lineage #swine #H1N1 virus in northern #China (Emerg Microbes Infect., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Emerg Microbes Infect. 2019;8(1):1535-1545. doi: 10.1080/22221751.2019.1679611.

Human infection with a novel reassortant Eurasian-avian lineage swine H1N1 virus in northern China.

Li X1, Guo L1, Liu C2, Cheng Y3, Kong M1, Yang L3, Zhuang Z1, Liu J3, Zou M1, Dong X1, Su X1, Gu Q1.

Author information: 1 Tianjin Centers for Disease Control and Prevention, Tianjin, People’s Republic of China. 2 Jizhou District Center for Disease Control and Prevention, Tianjin, People’s Republic of China. 3 Chinese National Influenza Center, National Institute for Viral Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China.



Influenza A virus infections occur in different species, causing mild to severe respiratory symptoms that lead to a heavy disease burden. Eurasian avian-like swine influenza A(H1N1) viruses (EAS-H1N1) are predominant in pigs and occasionally infect humans. An influenza A(H1N1) virus was isolated from a boy who was suffering from fever and headache and designated as A/Tianjin-baodi/1606/2018(H1N1). Full-genome sequencing and phylogenetic analysis revealed that A/Tianjin-baodi/1606/2018(H1N1) is a novel reassortant EAS-H1N1 containing gene segments from EAS-H1N1 (HA and NA), classical swine H1N1(NS) and A(H1N1)pdm09(PB2, PB2, PA, NP and M) viruses. The isolation and analysis of A/Tianjin-baodi/1606/2018(H1) provide further evidence that EAS-H1N1 poses a threat to human health and greater attention should be paid to surveillance of influenza virus infection in pigs and humans.

KEYWORDS: EAS-H1N1; Influenza A virus; Phylogenetic analysis; molecular characteristics; triple-reassortant

PMID: 31661383 PMCID: PMC6830285 DOI: 10.1080/22221751.2019.1679611 [Indexed for MEDLINE] Free PMC Article

Keywords: Influenza A; Swine Influenza; H1N1; H1N1pdm09; Reassortant strain; Human; China.


#Interspecies #Transmission of #Reassortant #Swine #Influenza A Virus Containing #Genes from Swine Influenza A #H1N1pdm09 and A(#H1N2) Viruses (Emerg Infect Dis., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Volume 26, Number 2—February 2020 / Research

Interspecies Transmission of Reassortant Swine Influenza A Virus Containing Genes from Swine Influenza A(H1N1)pdm09 and A(H1N2) Viruses

Helen E. Everett  , Bethany Nash, Brandon Z. Londt1, Michael D. Kelly, Vivien Coward, Alejandro Nunez, Pauline M. van Diemen, Ian H. Brown, and Sharon M. Brookes

Author affiliations: Animal and Plant Health Agency, Weybridge, UK



Influenza A(H1N1)pdm09 (pH1N1) virus has become established in swine in the United Kingdom and currently co-circulates with previously enzootic swine influenza A virus (IAV) strains, including avian-like H1N1 and human-like H1N2 viruses. During 2010, a swine influenza A reassortant virus, H1N2r, which caused mild clinical disease in pigs in the United Kingdom, was isolated. This reassortant virus has a novel gene constellation, incorporating the internal gene cassette of pH1N1-origin viruses and hemagglutinin and neuraminidase genes of swine IAV H1N2 origin. We investigated the pathogenesis and infection dynamics of the H1N2r isolate in pigs (the natural host) and in ferrets, which represent a human model of infection. Clinical and virologic parameters were mild in both species and both intraspecies and interspecies transmission was observed when initiated from either infected pigs or infected ferrets. This novel reassortant virus has zoonotic and reverse zoonotic potential, but no apparent increased virulence or transmissibility, in comparison to pH1N1.

Keywords: Swine Influenza; Influenza A; Reassortant strain; H1N1pdm09; H1N2; Pigs; UK.


Emergence of an #Eurasian #avian-like #swine #influenza A (#H1N1) virus from #mink in #China (Vet Microbiol., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Vet Microbiol. 2020 Jan;240:108509. doi: 10.1016/j.vetmic.2019.108509. Epub 2019 Nov 22.

Emergence of an Eurasian avian-like swine influenza A (H1N1) virus from mink in China.

Liu J1, Li Z1, Cui Y1, Yang H1, Shan H1, Zhang C2.

Author information: 1 College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China. 2 College of Veterinary Medicine, Qingdao Agricultural University, Qingdao, China. Electronic address: zhangchuanmei100@163.com.



We evaluated the phenotype and genotype of a fatal influenza/canine distemper virus coinfection found in farmed mink in China. We identified a novel subtype H1N1 influenza virus strain from the lungs of infected mink designated A/Mink/Shandong/1121/2017 (H1N1). The results of phylogenetic analysis of 8 gene fragments of the H1N1 strain showed the virus was a swine origin triple-reassortant H1N1 influenza virus: with the 2009 pandemic H1N1 segments (PB2, PB1, PA, NP and M), Eurasian avian-like H1N1 swine segments (HA and NA) and classical swine (NS) lineages. The EID50/0.2 mL of this strain was 10-6.2 and pathogenicity tests were 100 % lethal in a mouse model of infection. We found that while not lethal and lacking any overt signs of infection in mink, the virus could proliferate in the upper respiratory tracts and the animals were converted to seropositive for the HA protein.

Copyright © 2019 Elsevier B.V. All rights reserved.

KEYWORDS: Eurasian avian-like swine influenza virus; H1N1; Mink influenza virus; Phylogenetic analysis; Reassortment

PMID: 31902506 DOI: 10.1016/j.vetmic.2019.108509

Keywords: Avian Influenza; Swine Influenza; H1N1pdm09; H1N1; Reassortant strain; Wildlife; China.


Heterologous #Antibody Responses Conferred by A #H3N2v and Seasonal #Influenza #Vaccination against Newly Emerged 2016-2018 A H3N2v Viruses in Healthy Persons (Clin Infect Dis., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Clin Infect Dis. 2019 Dec 20. pii: ciz1203. doi: 10.1093/cid/ciz1203. [Epub ahead of print]

Heterologous Antibody Responses Conferred by A(H3N2) Variant and Seasonal Influenza Vaccination against Newly Emerged 2016-2018 A(H3N2) Variant Viruses in Healthy Persons.

Liu F1, Levine MZ1.

Author information: 1 Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.




Swine origin A(H3N2) variant (A(H3N2)v) viruses continue to evolve and remain a public health threat. Recent outbreaks in humans in 2016-2018 were caused by a newly emerged A(H3N2)v cluster 2010.1 which are genetically and antigenically distinct from the previously predominant cluster IV. To address the public health risk, we evaluated the levels of heterologous cross-reactive antibodies to A(H3N2)v cluster 2010.1 viruses induced from an existing cluster IV A(H3N2)v vaccine and several seasonal inactivated influenza vaccines (IIVs) in adults, elderly and children.


Human vaccine sera and ferret antisera were analyzed by hemagglutination inhibition (HI) and neutralization assays against representative A(H3N2)v viruses from clusters IV and 2010.1, and seasonal A(H3N2) viruses.


Ferret antisera detected no or little cross-reactivity between the two A(H3N2)v clusters, or between A(H3N2)v and seasonal A(H3N2) viruses. In humans, cluster IV A(H3N2)v vaccine induced antibodies cross-reactive to cluster 2010.1 viruses in about 1/3 of the 89 adult and elderly vaccinees. Seasonal IIVs did not induce seroprotective antibodies (≥ 40) to A(H3N2)v viruses in young children, but induced higher antibodies to A(H3N2)v viruses in cluster 2010.1 than those in cluster IV in adults.


Cluster IV A(H3N2)v vaccine did not provide sufficient heterologous antibody responses against the new 2010.1 cluster A(H3N2)v viruses. Seasonal IIV could not induce seroprotective antibodies to 2010.1 cluster A(H3N2)v viruses in young children, suggesting that young children are still at high risk to the newly emerged A(H3N2)v viruses. Continued surveillance on A(H3N2)v viruses is critical for risk assessment and pandemic preparedness.

Published by Oxford University Press for the Infectious Diseases Society of America 2019. This work is written by (a) US Government employee(s) and is in the public domain in the US.

KEYWORDS: A(H3N2) variant viruses (A(H3N2)v); HI and MN antibody responses; antigenic analysis; heterologous responses; influenza vaccine; seasonal Influenza A(H3N2) viruses

PMID: 31858129 DOI: 10.1093/cid/ciz1203

Keywords: Seasonal Influenza; Swine Influenza; H3N2v; Human; Vaccines.