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Population susceptibility to a variant swine-origin influenza virus A(H3N2) in Vietnam, 2011-2012.

Hoa LN, Bryant JE, Choisy M, Nguyet LA, Bao NT, Trang NH, Chuc NT, Toan TK, Saito T, Takemae N, Horby P, Wertheim H, Fox A - Epidemiol. Infect. (2015)

Bottom Line: Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants.Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009.These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

View Article: PubMed Central - PubMed

Affiliation: Oxford University Clinical Research Unit and Wellcome Trust Major Overseas Programme,Vietnam.

ABSTRACT
A reassortant swine-origin A(H3N2) virus (A/swine/BinhDuong/03-9/2010) was detected through swine surveillance programmes in southern Vietnam in 2010. This virus contains haemagglutinin and neuraminidase genes from a human A(H3N2) virus circulating around 2004-2006, and the internal genes from triple-reassortant swine influenza A viruses (IAVs). To assess population susceptibility to this virus we measured haemagglutination inhibiting (HI) titres to A/swine/BinhDuong/03-9/2010 and to seasonal A/Perth/16/2009 for 947 sera collected from urban and rural Vietnamese people during 2011-2012. Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants. Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009. These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

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Bayesian Markov chain Monte Carlo phylogenetic tree based on nucleotide sequences of H3HA genes of selected H3N2 viruses. The analysis was performed in Beast package v. 1.7.4(http://beast.bio.ed.ac.uk/) using 164 HA sequences (1701 bp) of H3N2 virusesisolated from 2000 to 2013. Node bars show the estimated divergent period to most recentcommon ancestor (95% highest posterior density).
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fig01: Bayesian Markov chain Monte Carlo phylogenetic tree based on nucleotide sequences of H3HA genes of selected H3N2 viruses. The analysis was performed in Beast package v. 1.7.4(http://beast.bio.ed.ac.uk/) using 164 HA sequences (1701 bp) of H3N2 virusesisolated from 2000 to 2013. Node bars show the estimated divergent period to most recentcommon ancestor (95% highest posterior density).

Mentions: In recent years, surveillance of swine influenza viruses in Vietnam has received muchattention, due to the perception of Vietnam as a ‘hotspot’ for viral emergence and theinherent dangers of co-circulation of highly pathogenic avian viruses (H5N1) in areas withdense poultry and pig populations. The first detection of human-origin influenza viruses inswine in Vietnam was a reassortant A(H3N2) (A/swine/BinhDuong/03–9/2010, and hereafterreferred to as Sw/VN10) found in 2010 from a commercial pig farm located in the southeastregion of Vietnam, to the north of Ho Chi Minh City [5]. Genetic analysis revealed that the six Binh Duong H3N2 swine viruses isolated atone time from the same farm had HA similar to human seasonal viruses circulating between 2004and 2006 (Fig. 1) [5]. The estimated time to most recent common ancestor of the Vietnamese swine-originBinh Duong H3 cluster suggested human-to-pig transmission in late 2004 (95% highest posteriordensity value, 23 October 2004 to 16 December 2004). Antigenically, Sw/VN10 exhibited aprofile that was distinguishable from contemporary human H3 viruses, but showed some level ofcross-reactivity with antisera of human seasonal vaccines and recent cluster variants (Table 1, e.g. 1:320 to A/Wyoming/03 and 1:140 toA/Wuhan/95). Although swine surveillance data from Vietnam is not available prior to 2010,Sw/VN10-like viruses were isolated each year from southern Vietnamese swine from 2010 to 2014,suggesting that it is has been one of the dominant contemporary swine IAVs circulating inVietnam, at least for the past 4 years. The human seasonal H3N2 viruses circulating in theregion during 2007–2008 were A/H3N2/Brisbane/10/2007-like, with a cluster transition toA/Perth/16/2009 (hereafter referred to as Pe09) in 2009 that has persisted until at leastmid-2013. Fig. 1.


Population susceptibility to a variant swine-origin influenza virus A(H3N2) in Vietnam, 2011-2012.

Hoa LN, Bryant JE, Choisy M, Nguyet LA, Bao NT, Trang NH, Chuc NT, Toan TK, Saito T, Takemae N, Horby P, Wertheim H, Fox A - Epidemiol. Infect. (2015)

Bayesian Markov chain Monte Carlo phylogenetic tree based on nucleotide sequences of H3HA genes of selected H3N2 viruses. The analysis was performed in Beast package v. 1.7.4(http://beast.bio.ed.ac.uk/) using 164 HA sequences (1701 bp) of H3N2 virusesisolated from 2000 to 2013. Node bars show the estimated divergent period to most recentcommon ancestor (95% highest posterior density).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595856&req=5

fig01: Bayesian Markov chain Monte Carlo phylogenetic tree based on nucleotide sequences of H3HA genes of selected H3N2 viruses. The analysis was performed in Beast package v. 1.7.4(http://beast.bio.ed.ac.uk/) using 164 HA sequences (1701 bp) of H3N2 virusesisolated from 2000 to 2013. Node bars show the estimated divergent period to most recentcommon ancestor (95% highest posterior density).
Mentions: In recent years, surveillance of swine influenza viruses in Vietnam has received muchattention, due to the perception of Vietnam as a ‘hotspot’ for viral emergence and theinherent dangers of co-circulation of highly pathogenic avian viruses (H5N1) in areas withdense poultry and pig populations. The first detection of human-origin influenza viruses inswine in Vietnam was a reassortant A(H3N2) (A/swine/BinhDuong/03–9/2010, and hereafterreferred to as Sw/VN10) found in 2010 from a commercial pig farm located in the southeastregion of Vietnam, to the north of Ho Chi Minh City [5]. Genetic analysis revealed that the six Binh Duong H3N2 swine viruses isolated atone time from the same farm had HA similar to human seasonal viruses circulating between 2004and 2006 (Fig. 1) [5]. The estimated time to most recent common ancestor of the Vietnamese swine-originBinh Duong H3 cluster suggested human-to-pig transmission in late 2004 (95% highest posteriordensity value, 23 October 2004 to 16 December 2004). Antigenically, Sw/VN10 exhibited aprofile that was distinguishable from contemporary human H3 viruses, but showed some level ofcross-reactivity with antisera of human seasonal vaccines and recent cluster variants (Table 1, e.g. 1:320 to A/Wyoming/03 and 1:140 toA/Wuhan/95). Although swine surveillance data from Vietnam is not available prior to 2010,Sw/VN10-like viruses were isolated each year from southern Vietnamese swine from 2010 to 2014,suggesting that it is has been one of the dominant contemporary swine IAVs circulating inVietnam, at least for the past 4 years. The human seasonal H3N2 viruses circulating in theregion during 2007–2008 were A/H3N2/Brisbane/10/2007-like, with a cluster transition toA/Perth/16/2009 (hereafter referred to as Pe09) in 2009 that has persisted until at leastmid-2013. Fig. 1.

Bottom Line: Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants.Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009.These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

View Article: PubMed Central - PubMed

Affiliation: Oxford University Clinical Research Unit and Wellcome Trust Major Overseas Programme,Vietnam.

ABSTRACT
A reassortant swine-origin A(H3N2) virus (A/swine/BinhDuong/03-9/2010) was detected through swine surveillance programmes in southern Vietnam in 2010. This virus contains haemagglutinin and neuraminidase genes from a human A(H3N2) virus circulating around 2004-2006, and the internal genes from triple-reassortant swine influenza A viruses (IAVs). To assess population susceptibility to this virus we measured haemagglutination inhibiting (HI) titres to A/swine/BinhDuong/03-9/2010 and to seasonal A/Perth/16/2009 for 947 sera collected from urban and rural Vietnamese people during 2011-2012. Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants. Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009. These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

Show MeSH
Related in: MedlinePlus