Historical #Origins and #Zoonotic #Potential of #Avian #Influenza Virus #H9N2 in #Tunisia Revealed by Bayesian Analysis and Molecular Characterization (Arch Virol., abstract)

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

Arch Virol. 2020 Apr 25. doi: 10.1007/s00705-020-04624-4. Online ahead of print.

Historical Origins and Zoonotic Potential of Avian Influenza Virus H9N2 in Tunisia Revealed by Bayesian Analysis and Molecular Characterization

Marwa Arbi 1, Oussema Souiai 2, Natalia Rego 3, Imen Larbi 1, Hugo Naya 3 4, Abdeljelil Ghram 1, Mehdi Houimel 5

Affiliations: 1 Laboratory of Epidemiology and Veterinary Microbiology, LR19IPT03, Institut Pasteur de Tunis, University Tunis El Manar, 13, Place Pasteur, BP74, 1002, Tunis, Belvedere, Tunisia. 2 Laboratory of Bioinformatics, Biomathematics and Biostatistics, LR16IPT09, Institut Pasteur de Tunis, University of Tunis El Manar, Tunis, Tunisia. 3 Bioinformatics Unit, Institut Pasteur de Montevideo, Mataojo 2020, 11400, Montevideo, Uruguay. 4 Departmento de Producción Animal y Pasturas, Facultad de Agronomía, Universidad de la República, Av. Gral. Eugenio Garzón 780, 12900, Montevideo, Uruguay. 5 Laboratory of Epidemiology and Veterinary Microbiology, LR19IPT03, Institut Pasteur de Tunis, University Tunis El Manar, 13, Place Pasteur, BP74, 1002, Tunis, Belvedere, Tunisia. mehdi.houimel@pasteur.rns.tn.

PMID: 32335769 DOI: 10.1007/s00705-020-04624-4



During 2009-2012, several outbreaks of avian influenza virus H9N2 were reported in Tunisian poultry. The circulating strains carried in their hemagglutinins the human-like marker 226L, which is known to be important for avian-to-human viral transmission. To investigate the origins and zoonotic potential of the Tunisian H9N2 viruses, five new isolates were identified during 2012-2016 and their whole genomes were sequenced. Bayesian-based phylogeny showed that the HA, NA, M and NP segments belong to the G1-like lineage. The PB1, PB2, PA and NS segments appeared to have undergone multiple intersubtype reassortments and to be only distantly related to all of the Eurasian lineages (G1-like, Y280-like and Korean-like). The spatiotemporal dynamic of virus spread revealed that the H9N2 virus was transferred to Tunisia from the UAE through Asian and European pathways. As indicated by Bayesian analysis of host traits, ducks and terrestrial birds played an important role in virus transmission to Tunisia. The subtype phylodynamics showed that the history of the PB1 and PB2 segments was marked by intersubtype reassortments with H4N6, H10N4 and H2N2 subtypes. Most of these transitions between locations, hosts and subtypes were statistically supported (BF > 3) and not influenced by sampling bias. Evidence of genetic evolution was observed in the predicted amino acid sequences of the viral proteins of recent Tunisian H9N2 viruses, which were characterized by the acquisition of new mutations involved in virus adaptation to avian and mammalian hosts and amantadine resistance. This study is the first comprehensive analysis of the evolutionary history of Tunisian H9N2 viruses and highlights the zoonotic risk associated with their circulation in poultry, indicating the need for continuous surveillance of their molecular evolution.

Grant support LR19IPT06/Tunisian Ministry for Research and Technology

Keywords: Avian Influenza; H9N2; Poultry; Reassortant strain; Tunisia; Antivirals; Drugs resistance; Amantadine.


#Influenza #Hemagglutinins #H2, #H5, #H6, and #H11 are not Targets of Pulmonary #Surfactant Protein D: N-glycan subtypes in host-pathogen interactions (J Virol., abstract)

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

Influenza Hemagglutinins H2, H5, H6, and H11 are not Targets of Pulmonary Surfactant Protein D: N-glycan subtypes in host-pathogen interactions

Lisa Parsons, Yanming An, Li Qi, Mitchell White, Roosmarijn van der Woude, Kevan Hartshorn, Jeffery K. Taubenberger, Robert P. de Vries, John F. Cipollo

DOI: 10.1128/JVI.01951-19



Seasonal influenza carrying key hemagglutinin (HA) head region glycosylation sites can be removed from the lung by pulmonary surfactant protein D (SP-D). Little is known about HA head glycosylation of low pathogenicity A type influenza virus (LPAIV) subtypes. These can pose a pandemic threat through reassortmant and emergence in human populations. Since the presence of head region high mannose glycosites dictates SP-D activity, the ability to predict these glycosite glycan subtypes may be of value. Here we investigate the activities of two recombinant human SP-D forms against representative LPAIV including H2N1, H5N1, H6N1, H11N9, an avian H3N8 and a human seasonal H3N2 subtype. Using mass spectrometry, we determined the glycan subclasses and heterogeneities at each head glycosylation site. Sequence alignment and molecular structure analysis of the HAs were performed for LPIAV strains in comparison to seasonal H3N2 and avian H3N8. Intramolecular contacts were determined between protein backbone and glycosite glycan based on available three-dimensional structure data. We found that glycosite “N165” (H3 numbering) is occupied by high mannose glycans in H3 HA but by complex glycans in all LVIAV HAs. SP-D was not active on LPAIV but was on H3 HAs. Since SP-D affinity for influenza HA depends on the presence of high mannose glycan on the head region our data demonstrate that SP-D may not protect against virus containing these HA subtypes. Our results also demonstrate that glycan subtype can be predicted at some glycosites based on sequence comparisons and three dimensional structural analysis.



Low pathogenicity A type influenza virus (LPAIV) subtypes can reassort with circulating human strains and pandemic viruses can emerge in human populations as was seen in the 1957 pandemic, where an H2 virus reassorted with the circulating H1N1 to create a novel H2N2 genotype. Lung surfactant protein D (SP-D), a key factor in first line innate immunity defence, removes IAV through interaction with hemagglutinin (HA) head region high mannose glycan(s). While it is known that both H1 and H3 HAs, have a key high mannose glycosite(s) in the head region, little is known about such glycosylation of LPAIV strains H2N1, H5N1, H6N1, or H11N9, which may pose future health risks. Here, we demonstrate that the hemagglutinins of LPAIV strains do not have the required high mannose glycans, do not interact with SP-D, and that sequence analysis can predict glycan subtype thus predicting presence or absence of this virulence marker.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Avian Influenza; Influenza A; Reassortant strains; H1N1; H2N2; H2N1; H3N2; H3N8; H5N1; H6N1; H11N9; Viral pathogenesis.


A live-attenuated #influenza #vaccine (#LAIV) elicits enhanced heterologous protection when the internal genes of the vaccine are matched to the challenge virus (J Virol., abstract)

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

A live-attenuated influenza vaccine (LAIV) elicits enhanced heterologous protection when the internal genes of the vaccine are matched to the challenge virus

Andrew Smith, Laura Rodriguez, Maya El Ghouayel, Aitor Nogales, Jeffrey M. Chamberlain, Katherine Sortino, Emma Reilly, Changyong Feng, David J. Topham, Luis Martínez-Sobrido, Stephen Dewhurst

DOI: 10.1128/JVI.01065-19



Influenza A virus (IAV) causes significant morbidity and mortality, despite the availability of viral vaccines. The efficacy of live attenuated influenza vaccines (LAIVs) has been especially poor in recent years. One potential reason is that the master donor virus (MDV), on which all LAIVs are based, contains either the internal genes of the 1960 A/Ann Arbor/6/60 or the 1957 A/Leningrad/17/57 H2N2 viruses (i.e., they diverge considerably from currently circulating strains). We previously showed that introduction of the temperature sensitive (ts) residue signature of the AA/60 MDV into a 2009 pandemic A/California/04/09 H1N1 virus (Cal/09) results in only 10-fold in vivo attenuation in mice. We have previously shown that the ts residue signature of the Russian A/Leningrad/17/57 H2N2 LAIV (Len LAIV) more robustly attenuates the prototypical A/Puerto Rico/8/1934 (PR8) H1N1 virus. In this work, we therefore introduced the ts signature from Len LAIV into Cal/09. This new Cal/09 LAIV is ts in vitro, highly attenuated (att) in mice, and protects from a lethal homologous challenge. In addition, when our Cal/09 LAIV with PR8 HA and NA was used to vaccinate mice, it provided enhanced protection against a wild type Cal/09 challenge relative to a PR8 LAIV with the same attenuating mutations. These findings suggest it may be possible to improve the efficacy of LAIVs by better matching the sequence of the MDV to currently circulating strains.



Seasonal influenza infection remains a major cause of disease and death, underscoring the need for improved vaccines. Among current influenza vaccines, the live attenuated influenza vaccine (LAIV) is unique in its ability to elicit T cell immunity to the conserved internal proteins of the virus. Despite this, LAIV has shown limited efficacy in recent years. One possible reason is that the conserved, internal genes of all current LAIVs derive from virus strains that were isolated between 1957 and 1960, and that – as a result – do not resemble currently circulating influenza viruses. We have therefore developed and tested a new LAIV, based on a currently circulating pandemic strain of influenza. Our results show that this new LAIV elicits improved protective immunity when compared to a more conventional LAIV.

Copyright © 2019 Smith et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.

Keywords: Seasonal Influenza; Vaccines; Reassortant strain; H1N1; H1N1pdm09; H2N2.


The #neuraminidase of A(#H3N2) #influenza viruses circulating since 2016 is antigenically distinct from the A/Hong Kong/4801/2014 #vaccine #strain (Nat Microbiol., abstract)

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

Nat Microbiol. 2019 Aug 12. doi: 10.1038/s41564-019-0522-6. [Epub ahead of print]

The neuraminidase of A(H3N2) influenza viruses circulating since 2016 is antigenically distinct from the A/Hong Kong/4801/2014 vaccine strain.

Wan H1, Gao J2, Yang H3, Yang S4, Harvey R5, Chen YQ6, Zheng NY6, Chang J3, Carney PJ3, Li X2, Plant E2, Jiang L2, Couzens L7, Wang C2, Strohmeier S8, Wu WW9, Shen RF9, Krammer F8, Cipollo JF4, Wilson PC6, Stevens J3, Wan XF10, Eichelberger MC7, Ye Z2.

Author information: 1 Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA. Hongquan.wan@fda.hhs.gov. 2 Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA. 3 Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. 4 Division of Bacterial, Parasitic and Allergenic Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA. 5 National Institute for Biological Standards and Control, Potters Bar, UK. 6 Department of Medicine, Section of Rheumatology, The University of Chicago, Chicago, IL, USA. 7 Division of Biological Standards and Quantity Control, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA. 8 Department of Microbiology, Icahn School of Medicine at Mount Sinai, New York, NY, USA. 9 Facility for Biotechnology Resources, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA. 10 Department of Basic Sciences, College of Veterinary Medicine, Mississippi State University, Starkville, MS, USA.



A(H3N2) virus predominated recent influenza seasons, which has resulted in the rigorous investigation of haemagglutinin, but whether neuraminidase (NA) has undergone antigenic change and contributed to the predominance of A(H3N2) virus is unknown. Here, we show that the NA of the circulating A(H3N2) viruses has experienced significant antigenic drift since 2016 compared with the A/Hong Kong/4801/2014 vaccine strain. This antigenic drift was mainly caused by amino acid mutations at NA residues 245, 247 (S245N/S247T; introducing an N-linked glycosylation site at residue 245) and 468. As a result, the binding of the NA of A(H3N2) virus by some human monoclonal antibodies, including those that have broad reactivity to the NA of the 1957 A(H2N2) and 1968 A(H3N2) reference pandemic viruses as well as contemporary A(H3N2) strains, was reduced or abolished. This antigenic drift also reduced NA-antibody-based protection against in vivo virus challenge. X-ray crystallography showed that the glycosylation site at residue 245 is within a conserved epitope that overlaps the NA active site, explaining why it impacts antibody binding. Our findings suggest that NA antigenic drift impacts protection against influenza virus infection, thus highlighting the importance of including NA antigenicity for consideration in the optimization of influenza vaccines.

PMID: 31406333 DOI: 10.1038/s41564-019-0522-6

Keywords: Seasonal Influenza; Influenza A; H3N2.


The 2nd #sialic acid-binding site of #influenza A virus #neuraminidase is an important determinant of the #HA-NA- #receptor balance (PLoS Pathog., abstract)

[Source: PLoS Pathogens, full page: (LINK). Abstract, edited.]


The 2nd sialic acid-binding site of influenza A virus neuraminidase is an important determinant of the hemagglutinin-neuraminidase-receptor balance

Wenjuan Du, Hongbo Guo, Vera S. Nijman, Jennifer Doedt, Erhard van der Vries, Joline van der Lee, Zeshi Li, Geert-Jan Boons, Frank J. M. van Kuppeveld, Erik de Vries, Mikhail Matrosovich , Cornelis A. M. de Haan

Published: June 10, 2019 / DOI: https://doi.org/10.1371/journal.ppat.1007860 / This is an uncorrected proof.



Influenza A virus (IAV) neuraminidase (NA) receptor-destroying activity and hemagglutinin (HA) receptor-binding affinity need to be balanced with the host receptor repertoire for optimal viral fitness. NAs of avian, but not human viruses, contain a functional 2nd sialic acid (SIA)-binding site (2SBS) adjacent to the catalytic site, which contributes to sialidase activity against multivalent substrates. The receptor-binding specificity and potentially crucial contribution of the 2SBS to the HA-NA balance of virus particles is, however, poorly characterized. Here, we elucidated the receptor-binding specificity of the 2SBS of N2 NA and established an important role for this site in the virion HA-NA-receptor balance. NAs of H2N2/1957 pandemic virus with or without a functional 2SBS and viruses containing this NA were analysed. Avian-like N2, with a restored 2SBS due to an amino acid substitution at position 367, was more active than human N2 on multivalent substrates containing α2,3-linked SIAs, corresponding with the pronounced binding-specificity of avian-like N2 for these receptors. When introduced into human viruses, avian-like N2 gave rise to altered plaque morphology and decreased replication compared to human N2. An opposite replication phenotype was observed when N2 was combined with avian-like HA. Specific bio-layer interferometry assays revealed a clear effect of the 2SBS on the dynamic interaction of virus particles with receptors. The absence or presence of a functional 2SBS affected virion-receptor binding and receptor cleavage required for particle movement on a receptor-coated surface and subsequent NA-dependent self-elution. The contribution of the 2SBS to virus-receptor interactions depended on the receptor-binding properties of HA and the identity of the receptors used. We conclude that the 2SBS is an important and underappreciated determinant of the HA-NA-receptor balance. The rapid loss of a functional 2SBS in pandemic viruses may have served to balance the novel host receptor-repertoire and altered receptor-binding properties of the corresponding HA protein.


Author summary

Influenza A viruses infect birds and mammals. They contain receptor-binding (HA) and receptor-destroying (NA) proteins, which are crucial determinants of host tropism and pathogenesis. It is generally accepted that the functional properties of HA and NA need to be well balanced to enable virion penetration of the receptor-rich mucus layer, binding to host cells, and release of newly assembled particles. This HA-NA-receptor balance is, however, poorly characterized resulting in part from a lack of suitable assays to measure this balance. In addition, NA is much less studied than HA. NA contains, besides its receptor-cleavage site, a 2nd receptor-binding site, which is functional in avian, but not in human viruses. We now show that this 2nd receptor-binding site prefers binding to avian-type receptors and promotes cleavage of substrates carrying this receptor. Furthermore, by using novel assays, we established an important role for this site in the HA-NA-receptor balance of virus particles as it contributes to receptor binding and cleavage by virions, the latter of which is required for virion movement and self-elution from receptors. The results may provide an explanation for the rapid loss of a functional 2nd receptor-binding site in human pandemic viruses.


Citation: Du W, Guo H, Nijman VS, Doedt J, van der Vries E, van der Lee J, et al. (2019) The 2nd sialic acid-binding site of influenza A virus neuraminidase is an important determinant of the hemagglutinin-neuraminidase-receptor balance. PLoS Pathog 15(6): e1007860. https://doi.org/10.1371/journal.ppat.1007860

Editor: Florian Krammer, Icahn School of Medicine at Mount Sinai, UNITED STATES

Received: January 3, 2019; Accepted: May 22, 2019; Published: June 10, 2019

Copyright: © 2019 Du et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: W.D. was supported by a personal grant from the Chinese Scholarship Council (file number 201603250057). M.M. was supported by the German Research Foundation (DFG) (SFB 1021, project B02). E.v.d.V. was supported by a grant of the Volkswagen Foundation. C.A.M.d.H. was supported by the Mizutani Foundation for Glycoscience. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Keywords: Influenza A; Pandemic Influenza; H2N2; Virology.


The molecular #basis for #antigenic #drift of #human A/ #H2N2 #influenza viruses (J Virol., abstract)

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

The molecular basis for antigenic drift of human A/H2N2 influenza viruses

M. Linster, E.J.A. Schrauwen, S. van der Vliet, D.F. Burke, P. Lexmond, T.M. Bestebroer, D.J. Smith, S. Herfst, B.F. Koel, R.A.M. Fouchier

DOI: 10.1128/JVI.01907-18



Influenza A/H2N2 viruses caused a pandemic in 1957 and continued to circulate in humans until 1968. The antigenic evolution of A/H2N2 viruses over time and the amino acid substitutions responsible for this antigenic evolution are not known. Here, the antigenic diversity of a representative set of human A/H2N2 viruses isolated from 1957 until 1968 was characterized. Antigenic change of influenza A/H2N2 viruses during the 12 years that this virus circulated was modest. Two amino acid substitutions, T128D and N139K, located in the head domain of the H2 hemagglutinin molecule were identified as important determinants of antigenic change during A/H2N2 virus evolution. The rate of A/H2N2 virus antigenic evolution during the twelve-year period after introduction in humans was half of that of A/H3N2 viruses, despite similar rates of genetic change.



While influenza A viruses of subtype H2N2 were at the origin of the Asian influenza pandemic, little is known about the antigenic changes that occurred during the twelve years of circulation in humans, the role of preexisting immunity and evolutionary rates of the virus. In this study, the antigenic map derived from hemagglutination inhibition titers of cell-cultured virus isolates and ferret post-infection sera displayed a directional evolution of viruses away from earlier isolates. Furthermore, individual mutations in close proximity to the receptor-binding site of the HA molecule determined the antigenic reactivity confirming that individual amino acid substitutions in A/H2N2 viruses can confer major antigenic changes. This study adds to our understanding of virus evolution with respect to antigenic variability, rates of virus evolution, and potential escape mutants of A/H2N2.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Influenza A; Seasonal Influenza; Pandemic Influenza; H2N2.


#H2 #influenza viruses: designing #vaccines against future H2 #pandemics (Biochem Soc Trans., abstract)

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

Biochem Soc Trans. 2019 Jan 15. pii: BST20180602. doi: 10.1042/BST20180602. [Epub ahead of print]

H2 influenza viruses: designing vaccines against future H2 pandemics.

Reneer ZB1, Ross TM2,3.

Author information: 1 Center for Vaccines and Immunology, University of Georgia, Athens, GA 30602, U.S.A. 2 Center for Vaccines and Immunology, University of Georgia, Athens, GA 30602, U.S.A. tedross@uga.edu. 3 Department of Infectious Diseases, University of Georgia, Athens, GA 30602, U.S.A.



Influenza-related pathologies affect millions of people each year and the impact of influenza on the global economy and in our everyday lives has been well documented. Influenza viruses not only infect humans but also are zoonotic pathogens that infect various avian and mammalian species, which serve as viral reservoirs. While there are several strains of influenza currently circulating in animal species, H2 influenza viruses have a unique history and are of particular concern. The 1957 ‘Asian Flu’ pandemic was caused by H2N2 influenza viruses and circulated among humans from 1957 to 1968 before it was replaced by viruses of the H3N2 subtype. This review focuses on avian influenza viruses of the H2 subtype and the role these viruses play in human infections. H2 influenza viral infections in humans would present a unique challenge to medical and scientific researchers. Much of the world’s population lacks any pre-existing immunity to the H2N2 viruses that circulated 50-60 years ago. If viruses of this subtype began circulating in the human population again, the majority of people alive today would have no immunity to H2 influenza viruses. Since H2N2 influenza viruses have effectively circulated in people in the past, there is a need for additional research to characterize currently circulating H2 influenza viruses. There is also a need to stockpile vaccines that are effective against both historical H2 laboratory isolates and H2 viruses currently circulating in birds to protect against a future pandemic.

© 2019 The Author(s). Published by Portland Press Limited on behalf of the Biochemical Society.

KEYWORDS: H2N2; influenza; pandemic; vaccine; virus

PMID: 30647144 DOI: 10.1042/BST20180602

Keywords: Pandemic Influenza; H2N2; Avian Influenza; Vaccines.


#Transmissibility and #severity of #influenza virus by #subtype (Infect Genet Evol., abstract)

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

Infect Genet Evol. 2018 Aug 10. pii: S1567-1348(18)30605-1. doi: 10.1016/j.meegid.2018.08.007. [Epub ahead of print]

Transmissibility and severity of influenza virus by subtype.

Park JE1, Ryu Y2.

Author information: 1 Korea Institute of Oriental Medicine, Daejeon, Republic of Korea; Center for Convergent Research of Emerging Virus Infection, Korea Research Institute of Chemical Technology, Daejeon, Republic of Korea. Electronic address: jepark@kiom.re.kr. 2 Korea Institute of Oriental Medicine, Daejeon, Republic of Korea.



The characteristics of influenza might vary depending on the disease subtype. This review includes previous studies on the transmissibility and severity of influenza and summarizes them by subtype. The attack rate and incubation period of influenza A were 2.3-12.3% and 1.4 days, respectively, and those of influenza B were 0.6-5.5% and 0.6 days, respectively. The five subtypes of influenza A virus, namely, H1N1, H2N2, H3N3, H5N1, and H7N9, are reviewed. The indexes related to transmissibility (reproduction number, attack rate, serial interval, latent period, incubation period, infectious period) and severity (hospitalization rate, case fatality rate) differed by influenza subtype. Generally, H3N2 showed a higher attack rate than H1N1 and H2N2. Additionally, H5N1 and H7N9 showed higher mortality rates than the other subtypes, including H1N1, H2N2, H3N2.

KEYWORDS: Flu; Impact; Influenza; Severity; Subtype; Transmissibility

PMID: 30103034 DOI: 10.1016/j.meegid.2018.08.007

Keywords: Influenza A; Seasonal Influenza; Pandemic Influenza; Avian Influenza; H1N1; H2N2; H3N2; H5N1; H7N9.


#Population Serologic #Immunity to #human and #avian #H2N2 viruses in the #USA and #HK for #Pandemic Risk #Assessment (J Infect Dis., abstract)

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

Population Serologic Immunity to human and avian H2N2 viruses in the United States and Hong Kong for Pandemic Risk Assessment

T M Babu, R Perera, J T Wu, T Fitzgerald, C Nolan, B J Cowling, S Krauss, J T Treanor, M Peiris

The Journal of Infectious Diseases, jiy291, https://doi.org/10.1093/infdis/jiy291

Published: 12 May 2018




Influenza A pandemics cause significant mortality and morbidity. H2N2 viruses have caused prior pandemic, and are circulating in avian reservoirs. The age-related frequency of current population immunity to H2 viruses was evaluated.


Hemagglutinin inhibition (HAI) assays against historical human and recent avian influenza A (H2N2) viruses were performed across age groups in Rochester, NY and Hong Kong, China. The impact of existing cross-reactive HAI immunity on the effective reproductive number(R) was modeled.


150 individual sera from Rochester and 295 from Hong Kong were included. 85% born in Rochester and Hong Kong before 1968 had HAI titers >1:40 against A/Singapore/1/57, and over 50% had titers >1:40 against A/Berkeley/1/68. The frequency of titers ≥1:40 to avian H2N2 A/Mallard/England/727/06 and A/Mallard/Netherlands/14/07 in subjects born before 1957 was 62% and 24%. There were no H2 HAI titers >1:40 in individuals born after 1968. These levels of seroprevalence reduce the initial R of A/Singapore/1/1957 or A/Berkeley/1/68 by 15%-20%. A basic reproductive number (R0) of the emerging transmissible virus less than 1.2 predicts a preventable pandemic.


Population immunity to H2 viruses is insufficient to block epidemic spread of H2 virus. An H2N2 pandemic would have lower impact in those born before 1968.

H2, pandemic, influenza, serology, effective reproduction number, pandemic risk assessment

Issue Section: Major Article

© The Author(s) 2018. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.

This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/about_us/legal/notices)

Keywords: Pandemic Influenza; Avian Influenza; Human; H2N2; Seroprevalence.


#Pandemic #Paradox: Early Life #H2N2 Pandemic #Influenza #Infection Enhanced Susceptibility to Death during the 2009 #H1N1 Pandemic (mBio, abstract)

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

Pandemic Paradox: Early Life H2N2 Pandemic Influenza Infection Enhanced Susceptibility to Death during the 2009 H1N1 Pandemic

Alain Gagnon a,b,  Enrique Acosta a, Stacey Hallman c, Robert Bourbeau a, Lisa Y. Dillon a, Nadine Ouellette a, David J. D. Earn d,e, D. Ann Herring f, Kris Inwood g, Joaquin Madrenas h, Matthew S. Miller e,i

a Department of Demography, Université de Montréal, Montréal, Canada; b Université de Montréal Public Health Research Institute (IRSPUM), Montréal, Canada; c Statistics Canada, Ottawa, Canada; d Department of Mathematics and Statistics, McMaster University, Hamilton, Canada; e Michael G. DeGroote Institute for Infectious Diseases Research, McMaster University, Hamilton, Canada; f Department of Anthropology, McMaster University, Hamilton, Canada; g Department of Economics and Finance, Department of History, University of Guelph, Guelph, Canada; h Los Angeles Biomedical Research Institute at Harbor, UCLA Medical Center, Los Angeles, California, USA; i Department of Biochemistry and Biomedical Sciences, McMaster Immunology Research Centre, McMaster University, Hamilton, Canada

W. Ian Lipkin, Editor

Author Affiliations: Mailman School of Public Health, Columbia University

Address correspondence to Matthew S. Miller, mmiller@mcmaster.ca.

Alain Gagnon, Enrique Acosta, and Matthew S. Miller contributed equally.



Recent outbreaks of H5, H7, and H9 influenza A viruses in humans have served as a vivid reminder of the potentially devastating effects that a novel pandemic could exert on the modern world. Those who have survived infections with influenza viruses in the past have been protected from subsequent antigenically similar pandemics through adaptive immunity. For example, during the 2009 H1N1 “swine flu” pandemic, those exposed to H1N1 viruses that circulated between 1918 and the 1940s were at a decreased risk for mortality as a result of their previous immunity. It is also generally thought that past exposures to antigenically dissimilar strains of influenza virus may also be beneficial due to cross-reactive cellular immunity. However, cohorts born during prior heterosubtypic pandemics have previously experienced elevated risk of death relative to surrounding cohorts of the same population. Indeed, individuals born during the 1890 H3Nx pandemic experienced the highest levels of excess mortality during the 1918 “Spanish flu.” Applying Serfling models to monthly mortality and influenza circulation data between October 1997 and July 2014 in the United States and Mexico, we show corresponding peaks in excess mortality during the 2009 H1N1 “swine flu” pandemic and during the resurgent 2013–2014 H1N1 outbreak for those born at the time of the 1957 H2N2 “Asian flu” pandemic. We suggest that the phenomenon observed in 1918 is not unique and points to exposure to pandemic influenza early in life as a risk factor for mortality during subsequent heterosubtypic pandemics.



The relatively low mortality experienced by older individuals during the 2009 H1N1 influenza virus pandemic has been well documented. However, reported situations in which previous influenza virus exposures have enhanced susceptibility are rare and poorly understood. One such instance occurred in 1918—when those born during the heterosubtypic 1890 H3Nx influenza virus pandemic experienced the highest levels of excess mortality. Here, we demonstrate that this phenomenon was not unique to the 1918 H1N1 pandemic but that it also occurred during the contemporary 2009 H1N1 pandemic and 2013–2014 H1N1-dominated season for those born during the heterosubtypic 1957 H2N2 “Asian flu” pandemic. These data highlight the heretofore underappreciated phenomenon that, in certain instances, prior exposure to pandemic influenza virus strains can enhance susceptibility during subsequent pandemics. These results have important implications for pandemic risk assessment and should inform laboratory studies aimed at uncovering the mechanism responsible for this effect.

KEYWORDS: influenza virus –  mortality –  pandemics –  susceptibility



Citation Gagnon A, Acosta E, Hallman S, Bourbeau R, Dillon LY, Ouellette N, Earn DJD, Herring DA, Inwood K, Madrenas J, Miller MS. 2018. Pandemic paradox: early life H2N2 pandemic influenza infection enhanced susceptibility to death during the 2009 H1N1 pandemic. mBio 9:e02091-17. https://doi.org/10.1128/mBio.02091-17.

Received 13 November 2017  – Accepted 22 November 2017  – Published 16 January 2018

Copyright © 2018 Gagnon et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license.

Keywords: Pandemic Influenza; H1N1pdm09; H1N1; H3N8; H2N2.