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.
Highlights
Surveillance of swine influenza viruses in Vietnam has received much attention, due to the perception of Vietnam as a ‘hotspot’ for viral emergence and the inherent dangers of co-circulation of highly pathogenic avian viruses (H5N1) in areas with dense poultry and pig populations
The first detection of human-origin influenza viruses in swine in Vietnam was a reassortant A(H3N2) (A/swine/ BinhDuong/03–9/2010, and hereafter referred to as Sw/VN10) found in 2010 from a commercial pig farm located in the southeast region of Vietnam, to the north of Ho Chi Minh City [5]
We aimed to investigate the susceptibility of the Vietnamese human population to Sw/ VN10 compared to contemporary circulating human H3N2 (Pe09) using serum collections from a previous comparative study of urban and rural residential populations [6]
Summary
Surveillance of swine influenza viruses in Vietnam has received much attention, due to the perception of Vietnam as a ‘hotspot’ for viral emergence and the inherent dangers of co-circulation of highly pathogenic avian viruses (H5N1) in areas with dense poultry and pig populations. The first detection of human-origin influenza viruses in swine in Vietnam was a reassortant A(H3N2) (A/swine/ BinhDuong/03–9/2010, and hereafter referred to as Sw/VN10) found in 2010 from a commercial pig farm located in the southeast region of Vietnam, to the north of Ho Chi Minh City [5].
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