ABSTRACT
To study influenza viruses in pigs in Sri Lanka, we examined samples from pigs at slaughterhouses. Influenza (H3N2) and A(H1N1)pdm09 viruses were prevalent during 2004-2005 and 2009-2012, respectively. Genetic and epidemiologic analyses of human and swine influenza viruses indicated 2 events of A(H1N1)pdm09 virus spillover from humans to pigs.
Subject(s)
Orthomyxoviridae Infections/veterinary , Respiratory Tract Infections/veterinary , Swine Diseases/virology , Abattoirs , Animals , Cell Line , Chick Embryo , Dogs , Humans , Influenza A Virus, H1N1 Subtype/isolation & purification , Influenza A Virus, H3N2 Subtype/isolation & purification , Orthomyxoviridae Infections/epidemiology , Orthomyxoviridae Infections/virology , Phylogeny , Prevalence , Respiratory Tract Infections/epidemiology , Respiratory Tract Infections/virology , Seroepidemiologic Studies , Sri Lanka/epidemiology , Sus scrofa/virology , Swine/virology , Swine Diseases/epidemiologyABSTRACT
To assess herd immunity to swine influenza viruses, we determined antibodies in 28 paired serum samples from participants in a prospective serologic cohort study in Hong Kong who had seroconverted to pandemic (H1N1) 2009 virus. Results indicated that infection with pandemic (H1N1) 2009 broadens cross-reactive immunity to other recent subtype H1 swine viruses.
Subject(s)
Influenza A Virus, H1N1 Subtype/immunology , Influenza, Human/immunology , Orthomyxoviridae Infections/immunology , Adolescent , Adult , Aged , Animals , Antibodies, Neutralizing/blood , Antibodies, Neutralizing/immunology , Antibodies, Viral/blood , Antibodies, Viral/immunology , Child , Cross Reactions , Hong Kong/epidemiology , Humans , Influenza, Human/epidemiology , Middle Aged , Orthomyxoviridae Infections/epidemiology , Pandemics , Swine/virology , Young AdultABSTRACT
Swine influenza A viruses (SwIV) cause significant economic losses in animal husbandry as well as instances of human disease and occasionally give rise to human pandemics, including that caused by the H1N1/2009 virus. The lack of systematic and longitudinal influenza surveillance in pigs has hampered attempts to reconstruct the origins of this pandemic. Most existing swine data were derived from opportunistic samples collected from diseased pigs in disparate geographical regions, not from prospective studies in defined locations, hence the evolutionary and transmission dynamics of SwIV are poorly understood. Here we quantify the epidemiological, genetic and antigenic dynamics of SwIV in Hong Kong using a data set of more than 650 SwIV isolates and more than 800 swine sera from 12 years of systematic surveillance in this region, supplemented with data stretching back 34 years. Intercontinental virus movement has led to reassortment and lineage replacement, creating an antigenically and genetically diverse virus population whose dynamics are quantitatively different from those previously observed for human influenza viruses. Our findings indicate that increased antigenic drift is associated with reassortment events and offer insights into the emergence of influenza viruses with epidemic potential in swine and humans.
